On that topic, I was on a business trip in the late '90s with my boss, who had graduated in '68. We were talking about casual dress, as our corporate HQ had just instituted "casual Fridays," which caused a negative stir among the elders. He noted that when he was in college in the northeast in the mid-to-late '60s the students wore jackets and ties to the football games. He said he went back for a game in '71 and all of a sudden none of the students were wearing that.
I filed that away. Many years later I saw footage of the epic Michigan-Ohio State game in '69, Schembechler's first year, when Michigan pulled the "upset of the century." Most of the students I could see in the background in Michigan Stadium were wearing coats and ties.
1970 seemed to be some sort of break point for casual dress among the young at college sporting events.