First and foremost, gambling is always depend on luck.
Gambling is definitely a game of luck. But here we are talking about sports betting. Sports betting can be considered as both game of luck and skill. As in sports betting you need to analyse the sports event, do calculations and then only bet in it. So if a bettor is losing, then it only proves that he doesn’t have required knowledge on that particular sport. To be honest, now for a few days I haven’t seen many gamblers losing money on sports betting, yes they bet on odds with less returns, but never seen losing more than winning.
In winning percentage you are right but in overall PnL, there’s still a lot of bettors on negative side since a one lose bet can give them a breakeven or lose even with multiple win depending on their odds choice.
I follow many popular tipster and most of theri winning rate is just ranging from 50% to 60+% at most. This will surely equivalent to losses if ever gambler that following this tipster bet equally.