Is there a specific context or field you have in mind? The terms refer to different things in the context of British politics, and many other countries too, so I'm not sure about the premise that their American connotations dominate(d). Or do you mean why do these terms, in American debates, refer to social policy instead of political theory etc?

Two days ago I gave an overview of how the term conservative came to refer to a distinctive political movement in America, which you may find useful too.

It seems the question of why ‘liberalism’ and ‘conservatism’ came to be seen as primarily social stances is also question of when this shift happened. If so, it becomes a relatively difficult question as to when exactly the ‘economic’ connotation of conservativism overtakes that of the ‘social’, something I imagine approaches like semantic analysis of newspapers, books etc. could help achieve. With that being said, the social – and to this, I’ll add, the moral – dimension of both conservatism and liberalism in the US really becomes quite pronounced, in what we might refer to colloquially as the rise of the ‘New Left’ or emergence of identity politics. I’m aware that being on the left =/= being liberal, but I sense that your question’s getting at why and how it was that these terms became chiefly social identifiers; I’ll also discuss why and when it was that conservatism could be economically liberal in some senses.

A recent overview of this is given in Andrew Hartman’s academic (but nonetheless quite readable) 2015 book, ‘A War for the Soul of America’. He traces the changing liberal and conservative debates to the 1960s. Hartman identifies the “culture wars” of this period as producing new visions of America that challenges quite fundamental ideas of community and individuality, and shifts ideas of the political from economic policymaking or even international relations and foreign policy to primarily about representation and identity – gender, religion, and race, which unfold culturally. Many histories of the ‘New Left’ in the 1960s or so usually suggest that this focus on identity and liberations as challenges to existing forms of identity and political organization when old methods fail – in Europe, this is often conceived as a crisis of Marxism, rooted in the failed realization of the May 1968 uprisings in France and the widespread publicity of the abuses of Stalinism from the circulation of books like the Gulag Archipelago. In America it’s antiwar movements, feminist, gay liberation, or Black Power movements – all with their own distinct histories that a short answer like this can’t really do justice to – that transforms ideas of what it means to be on the left. If he ubiquitous chanting at various political rallies – “it is forbidden to forbid!” or Jimi Hendrix represent an energized, popular wing of this social and cultural transformation of the left, it’s also important to bear in mind that this shift was also a serious political and intellectual one. Rationalistic views of human experience are also challenged. Hartman gives the example of Abraham Maslow, best known for his ‘hierarchy of needs’ – his elevation of “peak experiences”, hallucinatory emotional releases that cannot be reduced to rationalistic understanding, was a strong articulation by a respected psychologist that linked self-actualization to social openness and a rejection of traditional piety.

It’s against this perceived social transformation that writers like Irving Kristol and Daniel Bell come to articulate a form of neoconservatism in reaction against these claims from the left. The university was a key symbol of conflict, either as an institution promoting meritocratic acculturation into civilization and American values, or as a site to radically rethink questions of identity and structural justice. Allan Bloom (who’d claim to be neither conservative nor liberal even as he was firmly in the circle of neoconservatives), in the bestselling 1987 book Closing of the American Mind (and the namesake of that recent Atlantic article, the Coddling of the American Mind), attacked liberal academics for betraying liberal education – his own resignation from Cornell in the aftermath of death threats and demands when he shut down student protests. Another historian that writes very well about this is Daniel Rodgers in The Age of Fracture (especially the chapter ‘The Little Platoons of Society’) that charts a quickly-changing moral universe in the 1970s and 1980s. Like Hartman, he’s also an intellectual historian and engages in very close etymological analysis of how language use actually changes, particularly around concepts of the ‘civic’, ‘reason’, or ‘markets’.

Historian Jacob Hamburger notes the iron that “Bloom’s emphatically elitist book helped spark a decades-long wave of conservative polemics against the academic elite", as well as controversies around things like speech codes (introduced in 1988 at the University of Michigan) and the revision of curricula (as Stanford did in 1988 with its mandatory ‘Western Civilization’ course) that echo what we see today. I focus on Bloom because there is an interesting tension in his thought that suggests he’s concerned largely with the social, cultural and intellectual dimension of this conflict, less so the economics – he argues against the threat to American identity and education from "proponents of the free market", whose promise of social well-being "no longer compels belief" given that capitalist economies and the existing liberal-democratic order directed civic virtue towards mercenary ends and self-interest. Many don’t share this Socratic, ivory-tower view of universities and focus on education; debates about various other facets of “orderly society”, a recurring term in both popular and academic discourse, surround everything from television and advertising to employment and race. Religion (and here is where I disagree with Hartman’s analysis) is also significant in transforming the conservative-liberal debates: rather than an American court system that begins to ‘secularize’ in the 1980s (e.g the case of Bob Jones University v. United States), conservative pushes for ‘secular humanism’ to be defined as a ‘religion’ are compatible with how a Christian Right often benefitted from ‘secularizing’ itself as it expanded throughout society and introducing a complexity to the kind of “white Protestant moral authority” (in Hartman’s words).

Another thing that many histories of this period neglect, but I think is quite important in explaining the prominence of the social dimension to liberal and conservative discourse, are queer communities. Conservative politics marginalized various sexual minorities, as Lisa Szefel [reminds us](https://www.pacificu.edu/sites/default/files/faculty/Age%20of%20Fracture.pdf), and the AIDS crisis of the 1980s onwards was both an incredible tragedy of human life and an ‘epidemic of signification’ (as Szefel cites Paula Treichler). Hence queer politics particularly its antipathy animated by evangelical and Catholic thought and the polemics from neoconservatives, provide another anchor to understand the emerging significance of political discourses.

(con'td)