Because the other sports are considered “cooler” in the modern community. More flash and bigger bucks.
I’ve seen black men who are former baseball players and they swear that baseball has the better package (retirement and post 9-man career). Whether you become a scout, coach, or elsewhere in a franchise or the League.
I think they said on average the salaries are higher in MLB than the NFL or NBA but I don’t recall and that was probably around 5 years ago I heard them talking at a sportswriters dinner.
Post covid and woke those salaries are gonna take a hit. It will be interesting to see how hard. Sports will be living in interesting times.