With correct play slots have some of the lowest house edges per dollar bet. Sports betting has a fairly high edge, 4.5% on normal bets and much higher on exotics. The difference is you make a few sports bets and walk away, while with slots you keep cycling money through until you lose it.

The problem indeed is the small cycle time. If you bet on a sports match with a 4.5% expected loss, then watch the game, you can limit your losses to about 4.5%/hour.

A slot machine with an expected per iteration loss of .1% and a modest 100 iterations/hour, would, over that same hour lose you (just) go over 9%.