Well when you think of cycling you might think fun times riding with your family and friends just for an hour then go home, well when you’re competitive it’s not like that it’s hours on the bike riding with 50+ cyclists in one bunch and if you lose focus in may cost you a win an even the competition, crashes, injuries those are just the few things you have to deal with.
If you go to ride your bike just for fun you wouldn’t really have these things to deal with of course you could suffer and be sore and crash but it’s not as frequent, remember when you’re on a grand tour if you crash you have to ride the next day which will probably be really hard and if you ride for fun you can rest as much as you want.
Cycling demands a lot of experience and focus.