Most of the sites requiring KYC from their customers are really not legit and should be taken with caution. A lot of them are anonymous so how can they require their clients to accomplish KYC requirements? In this digital age, being anonymous is easy but building the reputation and credibility is hard.
brokers in specific would really love to not apply KYC since they have nothing to worry about regarding sharp bettors and they won't lose money anyways
so they would love to make it much easier to use them , but sometimes they are forced to do that due to laws
some brokers will allow you to use bitcoin with no KYC but as AC88 stated sometimes the books that they offer ask for that info so even the no KYC brokers may ask for that any moment
odyssey is great with that matter , the only thing to worry about is that they aren't really that old and they aren't as trusted as other brokers
if they keep running good for the next 2 years or so I guess all bitcoin users who use brokers will shift to it