First off, they used to be even wider in college than they are now (same with the uprights). that change was l992.
pros want more balance, NCAA favored offense w greater strong/weakside opportunities. I remember reading hashmarks debuted in an early 1930s pro football game played indoors. I also recall NFL changed their hashmarks in the early 70s which is when they were then narrower than college.
I will tell you the Option offenses loved wide hasmarks. college of course is older than pro ball, and until the late 50s/into 60s, college was a bigger deal.