I have used Strava since 2013 and upgraded when they presented that option. I don't worry too much about KOMs with other riders or runners, but I do like the personal PR kicks that Strava shows me.

As a Zwift user on the bike and running when weather doesn't cooperate with outside activities I also like that I can upload my 'virtual' runs and rides automatically to Strava also.

Also I like being able to search the app for some routes or race events to get a preview of the elevation changes.