Casino bonus forfeiture: why do sites take bonuses back

Had a bit of a headache recently where my bonus was just wiped from my account out of nowhere. No warning, nothing shady on my end, but I’d hit a win and was hoping to grind it through the wagering. Instead, poof - gone. I read through the terms again and saw stuff about max bet restrictions and timing, but it still feels random sometimes. Anyone else feel like the “forfeiture” part is always a bit murky, like sites just pull that card whenever they want?

Especially stings when you’re doing everything right with your play, like sticking to strategy and not going near roulette or slots when it’s a blackjack bonus. Curious if this is just the risk we take or if I’m missing something obvious.