What’s the problem with dating gym partners?

I’m probably gonna get a lot of hate for this but I genuinely don’t understand what’s wrong with dating the people you roll with or lift with. Like if they’re good people how does it Matter? I mean I’ve dated guys from my gym and we’re mature adults who handled it quite well. Eventually one of them left the gym coz of work. But before that there was no awkwardness or bad relations. I feel as long as you’re MATURE ADULTS it shouldn’t pose a problem.