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.
Sorry for getting off-topic, but RPS is very easy to make provably fair. In fact I do it all the time. Here's a good example of me playing in a provably fair way (for both of us) just using this forum: https://bitcointalk.org/index.php?topic=1588904.0 and includes a lot of explanation of how it works
Disclaimer: I'm down like 15 BTC net
Fuck RPS