Particularly in stadiums in the United States, every stadium is INCREDIBLY loud. It is well understood that any sound over 75 dB is considered dangerous and harmful to one’s ears, and stadiums are regularly at something like 100+ dB, probably like 110 – 120 at times.
Basketball players, for instance, play all of their games in enclosed arenas that are likely even louder than open-air stadiums (but also, maybe they aren’t??). A regular season of basketball is 82 games, plus potentially 28 more in the playoffs, and they’ll play for 15ish seasons, racking up well over a thousand instances of being in this extremely loud environment. As far as I know, players do not wear any sort of hearing protection at all, and they wouldn’t be encouraged to do so either since they need to hear things down on the playing field / court / etc.
So why have there not been widespread reports of massive hearing loss / tinnitus / any other number of hearing problems from professional athletes?