Part of it is the ubiquity of advertising, and the ability to gamble from anywhere using your phone. Both of which make it much easier to develop a gambling addiction, and much harder for and addict to stop gambling.

Sports betting also has the unique issue of introducing corruption into sports. A league like the NFL has a huge number of players, coaches, referees, and league staff, all of whom can influence the outcome of a game, and all of whom are potentially susceptible to bribes. A notable case of this happening is the "Black Sox" scandal, where the 1919 Chicago White Sox blatantly threw the World Series in exchange for bribes from a gambling syndicate. The more prolific sports betting is, the more likely events like this are.