Is watching a show with a female protagonist the same? Games are no different. You just control the character.
is playing theater just about speaking remembered texts? If that would be true you would never seen Joker hospital scene at all.
Yup, it begins with just "I control the character". But it goes a LOT deeper. Well, there is really no reason for that for in singleplayer games. Or standard MMO's. As your character is railroad to engine and script usually so no room for own decisions. So you never reach that because nothing forces you.
But when start with RP and move from light RP more to hardcore one you will feel that need to improve and to let your character make decisions not you. And this is part of any good story when it needs to be believable. After that you even sense if writer writes his story (quests in games f.e.) just by putting letters down or if he actually describe another reality where he was.
Because if you only control your toon you just run throu isometric forest looking for red creature to get more xp. If you let your character do it he walks throu the forest, he feels the morning wind, he sees the bark on the tree and he avoids that big ants lair as he has no intention disturbing their everydays work. He is there for gathering some mushrooms for experiments.