Why deposit money on a casino when you aren't ready to play with it? That's not good, so if I recommend any casino with vault features for you now you will store your crypto assets on such storage? Or the money you win from the casino? It's like entrusting your wins back into the hands of the people you won the money from, I don't like the sound of it.
it might safe funds from betting large amount by mistake.
This is the main reason why vault was introduced. Some gambler usually becomes greedy on their bet when adrenaline rush kicks in that sometimes makes them bet carelessly and lose all even with huge bankroll. Vault was introduced so that gambler can make part of their bankroll partially inaccessible to avoid betting error.
Also some vault offer different layer of protection which gives extra protection for user funds once they want to left the funds on casino account to save time and fee when they want to play again.