The problem with rock paper scissors (and poker for that matter) is that you don't know if the person you are playing against is another human (or bot) or are you playing against the house who can see your hand. You don't know if your hand is known to other person or not, it is not provably fair at all so at the end of the day you are not sure if you are being scammed or not. Even if the website is as legit as it gets, there is no written proof of it so you are still unsure about what you are doing and if the other person knows it.

Bustabit is one of the most trustworthy websites out there in the crypto world and I would still be skeptical about playing in a place with no provably fair rock paper scissors, maybe for fun but definitely not to win because there is no house edge (maybe rake) in there so you could actually profit but without provably fair I still wouldn't dream about profiting.