I have been reading a history of baseball written around 1910 that said that gambling was a big problem in the early days of baseball and was commonplace at ballparks during games in the 1870s. It was implied that the problem was gone, but obviously it was not. If they could forget the lessons of history back then, it could happen again.
Of course, players are much better paid now and less likely to be tempted, and it’s much harder to keep things under wraps nowadays. But for people like Rose, who are addicts, even being well paid cannot overcome the temptation.