why do some crypto casinos have worse odds than others

So I've been bouncing around a bunch of different crypto sites for roulette and slots lately and I've noticed the odds or RTP on certain games can be way off from others. I get that with provably fair stuff, but sometimes you’ll see the same provider’s slot on different sites, and the payout rate’s just straight up lower. Then you got original in-house games that feel just brutal on variance compared to the regular ones.

Is this just a licensing thing or are some casinos tweaking things behind the scenes? Kinda makes me hesitant to stick with any one spot too long. Curious what everyone else thinks or if you just play whatever’s got the best promos.