Do you care about the bonuses casino offers or play regularly and spotaneously without look at it like me ?
Don't get fussed with bonuses unless they are match deposit bonuses with (NO) playthrough requirement.
Maybe the OP is talking about Signup Bonuses and Free Rolls and give aways. its a good marketing campaign to get visitors to try their casino before going in for a big bank roll.
Usually what I get in emails as promos are free spins of slots which I mostly ignore.
If sometimes I try my lucky I never understand what is going on, just choose number of lines and amount and then rest I do not know. All I know is I never won anything really from bonuses.