If a player is gambling, that brings in the question of fixing games. If the public's perception is that your sports's games are fixed, you cease to be a sport and become WWE.
I think, at least in my opinion, most Pro Sports are more entertainment and less sport anyway.
This is from a google search "what sports does Draft Kings sponsor"
DraftKings is both an official daily fantasy and sports betting partner of the NFL, NHL, PGA TOUR, and UFC, as well as an official daily fantasy partner of NASCAR, an official sports betting partner of the NBA and an authorized gaming operator of MLB
How the hell you gonna take a sponsorship from a SPORTS BETTING COMPANY and then be so up in arms and offended when your players make bets??
I get it back in the 80's when Sports Betting was completely frowned upon and you had to use illegal bookies to make your bets. but 40 years later you're cashing checks from LEAGL BOOKIES and still calling Pete Rose a disgrace and not letting him in the HOF. Very hypocritical and asinine IMO.