Valid actions in OpenAI Gym

Question

Why don't the gym environments come with "valid actions"? The normal gym environment accepts as input any action, even if it's not even possible.

Is this a normal thing in reinforcement learning? Do the models really have to learn what valid actions are all the time? Would it not be much nicer to have a env.get_valid_actions() functions so that the model knows what actions are doable? Or is this somehow possible and I'm missing it?