Is it possible that it still counts as "putting on airs" even when done by academics?

I had a long stint in academics as both a student and as research staff, and I noticed many instances of unchallenged self-aggrandizement within that community. I could easily believe this to be another instance of that, even if institutionalized.

Edit: FWIW I haven't looked into this history of this particular topic. There may a respectable explanation and I'm just ignorant.

In general this is done out of an appreciation that no work exists in a vacuum. "We", takes away from the individual and attributes the work to a group of people, even if they are not coauthors. I actually think this is one of the better conventions in academia.

Well it is also worth mentioning, the "we" can be used as a way to give a paper a conversational tone whilst still remaining formal. The "we" in that kind of case is the other domain experts reading the paper the author is assuming they are speaking to.