There are SEVERAL hotels that require you to be a quest of that hotel to access the pool. Other than value resorts, the gate acts as a barrier between us and them to limit the amount of people in the pool at one time. With that being said, there are plenty of people the casually wait around and act like they are doing something until a guest of that hotel accessing the gate and the non-guest walks in behind them. Not saying to do this, only that it is being done now.
BUT for Yacht/Beach Club, you do need a wristband to go down the waterslide as there is a guard at the top.