Out of all the runners who were on your track or XC teams, how many were still running 10-ish years after graduation? What about ~20 years?
I graduated college in 2013. If I had to guess, approximately 10% are still running competitively now. Around 50% are hobby joggers, and the remaining 40% are non-runners but do some other sport or active hobby. I don't know anyone who became completely sedentary.