Yes, footballers can be pretty thick. You're expected not to let the team down, maybe it's taken a while to get your chance to impress, and sometimes that means missing months because you played on with a problem that might have lasted a few days. Kukharevych last season, for example. Brandon Cooper when on loan at Swindon. How many players do you see pull a hamstring and want to go back on, only to go down again next time they attempt a sprint? Fact is most players are playing through some pain most of the time, and knowing what needs treatment in the moment is difficult.
Timewasting existed but solving it means putting players at more risk, unfortunately.