A slot machine's payout changes all the time, but it's still not worth it to feed it quarters. If it paid out the probability-weighted average of what you would expect it to pay out every time (that is, slightly less than you put in), nobody would play. Introducing randomness makes it highly attractive despite still being a terrible deal.

Like car doors and ovens, there's rarely any marginal benefit from checking Facebook fifty times a day instead of twice a day, or at least no benefit that outweighs the opportunity cost of constant checking. It's a slot machine that you play with attention instead of money, which is just as bad if you assign any reasonable financial value to your time.