I'm sure this is the case with some - but for me, it's about giving my kids opportunities. I acknowledge and accept there a very small chance my kids ever play beyond say a university level - but if they fall in love with a sport and show a desire to get better and push themselves - I won't hold them back (unless I ultimately can't from a financial perspective).
There are simply too many positive life lessons you learn from rep sports. Kids internally pushing themselves, practicing to get better, hard work, teamwork and the ultimate reward to winning when you put in the hard work is something you carry for life. There are also lessons learned when cut from the team - or from losing the big game. This new thinking that simply participating is all you need to do is utter nonsense IMO.