For a more specific response to your question, if you have JSTOR, I would recommend the following review, Clark, Gregory. “A Review of Avner Greif's "institutions and the Path to the Modern Economy: Lessons from Medieval Trade"”. Journal of Economic Literature 45.3 (2007): 725–741.

It's about a book called Institutions and the Path to the Modern Economy, Lessons from Medieval Trade (obviously). The reviews are by historians that are greeted with the question of economic theory fairly recently. This review, also on JSTOR, is a little easier to digest and is by a cultural historian, Kathryn Reyerson. The Journal of Economic History 66.4 (2006): 1080–1081.

Edit: I think this lengthy excerpt from the second review kind of answers the question for someone like me, who is interested in economic problems but not in love with the application of economic methods:

The book suffers from a lack of nuance, as in the treatment of slavery, which did not disappear from medieval Europe as Greif states. Occasional anachronisms such as the use of the term Holy Roman Empire in an eleventh-century context creep into the text. The Assignment of Venetian origin for double-entry bookkeeping would entail more than a passing commentary as proof. Inn an otherwise interesting development on the perhaps unique European community responsibility system, the policing mechanism of the Champagne fairs-impounding or distraints and holding ‘every member of a community liable for each member’s default in intercommunity exchange’- could have effectively linked to a treatment of the law of marque (p. 328).

Elements of this kind of tap into my own prejudice for this kind of history. There is a sloppiness to actually getting the minutiae correct, evident in the first half of the quote. Double entry book keeping is a Florentine development (maybe). In the bolded section, he ignores a more legal approach. I think it's a fine book, but I have huge reservations is the way I, as more of a social historian, look at a lot of hard core economic history.

The "why" is not really a question with a factual (rather than polemical) answer. However, within Economic History, as practised largely within Economics departments rather than History in the US, and as a separate discipline of history in the UK, Fogel and Cliometrics are very much not ignored. Empirical analysis of historical data using econometric methods (a la Fogel) has become one of the predominant methods of doing Economic History.

For an overview, and a better informed view than mine, here's a working paper by Naomi Lamoreaux (Yale), a leading economic and business historian working in a history department, on the history of economic history in the US: http://economics.yale.edu/sites/default/files/files/Faculty/Lamoreaux/beyond-old-2015.pdf