I think stake have some kind of incentives for KYC-ed customers. For example some promotions are only available for level 2 verified players, for other you receive double the reward if verified.
Yes, it's a lucrative incentive, isn't it? Moreover, they get a second time reward, of course there will be many users flocking to do it so it will not be surprising if KYC has now become commonplace in casinos.
I even saw that with a higher VIP level and he had not done KYC then at that time if I'm not mistaken $250 will be incentivized by Stake.