There's been a general trend of grade inflation in U.S. universities, accelerating in the 1960s (during the Vietnam war), and then again in the 1990s [0]. In some sense, this might be because the role of the student shifted more towards that of a consumer purchasing a product.

Harvard average GPA was a 3.0 in 1967, now it's a 3.45 [1].

There are some universities that have tried to actively prevent inflation (e.g. Purdue with a 2.73 average in 1986 to 3.09 in 2012 [2]).

[0] https://www.gradeinflation.com [1] https://www.gradeinflation.com/Harvard.html [2] https://www.gradeinflation.com/Purdue.html