Yes! I hate the fact that everyone is constantly working to get that 20 in their respective "main stat"!
Make lvl 1 stats be the "peak" physical and mental abilities that the PC is capable of, and nothing short of magic can make them go up further.
Or, alternatively (and I'm shamelessly stealing/modifying this from The Black Hack here) have players at levelup roll a d20 for each stat (in any order they want). If the roll comes up ABOVE their current stat, they get an increase. But you can only get one stat incease per levelup (hence the "roll in any order") This way you get the occasional ASI but it gets increasingly harder the better your stats are.