Because it is your game.
But seriously, what kind of a dumb philosophical question is that. Why play any game? Or why play any fps game other then the one you already played?
Why try new food, if you can have pizza everyday.
Why bake your own pizza, if you can just order some.
Why even create any game? All has already been done this way or another. It is so repetivite, that we can identify tropes happening or codify a game/movie/story in such a way, that you only need to change a few words to have the same description for several things, makeing it seem like they are plagarisms.
But back to your question, for the same reason, they would watch your holiday pics you try to show them. Demanding that your single developer game has anything to offer in terms of competition against AAA games, is a bit much to ask. If you make an RPG they compare it with Baldur's Gate 3, I imagine.
Oh, and the best game of that type I know, is Hidden&Dangerous. (Disclaimer: I do not know all games ;-) )