The Marxist thing is a bit of a red herring (heh, get it? "red") since Paul Kirchhoff also coined the term "Mesoamerica," which enjoys widespread use. If anything, region and language are probably the more important reasons for it's lack of popularity in English language texts; it enjoys relatively greater popularity in Spanish language writings. López Austin & López Luján's El Pasado Indígena, one of the best general Spanish language general histories, uses the terms early on as geocultural framing device.

The other issue is that while "Mesoamerica" gained linguistic currency as a way to avoid awkwardly referring only to "Mexico" or "Central Mexico and the Maya Regions," or various other configurations, the main area of Oasisamerica had an extant rival: the Southwest. I would wager this at least partially accounts for the greater usage in Mexican publications, since the "Southwest" would be Oaxaca and Guerrero. Moreover, the term tends to gloss over the important connections and continuities with Northern and particularly Northwestern Mexico. If the prominence of "Southwest" then seems excessively US-centric (American, even), you need to keep in mind that the area had long been a source of anthropological interest. Some of the core founders of American Anthropology (Hrdlicka, Boas, and particularly Kroeber) had done work in the "Southwest."

So when Kirchhoff proposed the terms Aridoamerica and Oasisamerica (1952) to describe a broad swathe of non-agricultural peoples in arid environments and polynucleated group of sedentary farmers among them (to simplify the position), he was going against established terminology. He himself eased into the terms, referring to the "Greater Southwest" before making his arguments for his own subdivisions.

Perhaps the final barrier though, was that coming up with these kind of broad "culture areas" to be placed on maps was falling out of favor of a more nuanced and less static approach. Ironically, Kroeber (a proponent of the concept as originally established by his mentor, Boas) touched on some of the problems with the approach in his comment on Kirchhoff's paper: The boundaries shift, subsistence changes, myths and religious practices spill between areas, language bleeds out, etc. Culture areas are still taught today as a concept to Anthro students, but with the understanding that they are messy approximations. Kirchhoff's paper even contains some of these complications, as he grapples with how to classify semi-sedentary "part-farmers" on the edges of Oasisamerica and Mesoamerica. With our knowledge of archaeology today, we can see how interactions between the settled peoples of those two regions and the more nomadic Aridoamericans separating them were much more complex and intertwined than Kirchhoff's original delineation gives credit to.

The anthropological complications of the terms could have been refined more thoroughly, and to some extent they have, but nowhere near to the extent that the more widely adopted "Mesoamerica" has been. Kirchoff's original formulation of that culture area also had numerous glosses and oversights that have since been patched by innumerable academics working within that linguistic boundary. Using Arido- and Oasisamerica isn't going to throw an (academic) audience into confusion and panic, but the terms do lack the quick and easy recognition of Kirchhoff's more popular contribution to the terminology.

Anyway, I'm not surprised you heard it from a UNAM professor, since Kirchhoff taught there and was foundational to their Anthro program.

Politics, like nationalism, ruins all good history.

Imagine this - you have a degree in, for example, Indigenous American Art... But the university you got your degree from affixed the term 'Marxist' to most of it's degree programs. There are plenty of institutions and think-tanks that are going to value your opinion less - or perhaps more - simply because of that association, places that won't hire you, and people who will champion your theories or decry them without bothering to consider them.

Similarly, say you are essentially apolitical, perhaps even favoring Marxism, Third-Wayism, Anarchism or some other viewpoint, but you manage to score several lucrative book and lecture deals, then find yourself in an area whose academics were steeped in what is mostly the same history you were... But consider your decisions, however motivated by pragmatism, to have marred the credentials of your scholarship.

We all have biases, and most good historians try to acknowledge theirs. But the unfortunate reality is that many disciplines are still splitting hairs over infinitesimally unimportant doctrinal disputes.

Given that the terms are apolitical, though I am sure all parties could find a way to make them so, if I had to hazard a guess it would be the academic equivalent of throwing spitwads at one another. I am not a geologist or familiar with pre-contact Mesoamerica to any great extent, however - there could be more to do with the proponents other credentials for example.

There are plenty of other possible reasons however. For one, many such generalizations are just that, generalizations, and loathe to be adopted by the greater community as a whole. I know the various 'regions' of America still gets more eye-rolls from professors I know then acceptance, even more so as time goes by.

It could be that time and topography changed, and the term does not apply at all times, rendering it less useful and too specific to be of value for all but more limited studies.

Or it could be that the term has simply not been popularized enough and most people are genuinely confused by it. It is strange to think about but a lot of the terms we use are actually themselves relatively new. I would actually be interested in hearing more about this, if it's acceptable reddiquete to elaborate on a question? They both sound look fairly interesting blanket terms.