In house games have a house edge of 2%, while slots usually have an edge of at least 3-4%. The house edge difference doesn't fully account for the 2.8x difference, but I think they also want to reward actual players more than miners (who might just spam 1.05x dice to mine tokens) as they don't provide a good long term revenue stream.
Ever since casinos were ever created this happened, when the first crypto casinos like primedice started first thing people did was build bots that would abuse the faucet system, back in those days it was giving 10k per faucet claim and you could refresh for a new account so it was basically just a click memorizer as a bot and people claimed a lot of bitcoins, sure bitcoin wasn't this high on price but it was abused.
Long story short there are people who do 1.05 and try to mine tokens for sure, that will always be there, and whatever a casino does, you can't keep those people away, you will get them one way or another, they will always find a way to get in.