So, yes, the fact that the drinking age was 21 didn't prevent me from consuming excessive quantities of alcohol during my first three years of college¹, but it also eliminated differential situations like Illinois-Wisconsin which had a measurable impact on reducing DUI fatalities, so it was a bit more than not much.
---
1. During the late 80s, the dorm soda machines were stocked by the students. Many of the machines had a slot dedicated to beer (often a "random" slot where you took your chances. You might get something good, you might get Coors Light. The soda machine of the era were capable of dispensing glass bottles of beers even though they were designed for cans. Mostly capable. Occasionally, your 60 cents would end up buying you a pile of broken glass and beer foam. Regardless, having campus being the only place to feasibly buy alcohol meant that drunk driving incidents were rare to non-existent.