Because they will always move the goalposts. They relish and absolutely delight in seeing you unhappy and seeing you try to please them. That's the end game for them, and they're having tons of fun. Why would they give up their favourite game just so you can feel better about yourself? They don't care how you feel. They may be incapable of caring how anyone but themselves feel.
I promise it gets better, and you already have some sort of understanding of their abusive behaviour. I too almost killed myself because I never felt good enough. Please feel welcome to PM me if you ever want to talk more, or just to vent. I can understand, to a certain extent.
I'm a much much happier adult now, with VLC. My heart aches for teenage me. It was such a dark and difficult time and so incredibly lonely. Trying to be someone else, trying to punish yourself, and trying to take responsibility for your abuse are all signs that you're not the problem. You're not, I promise. Don't believe that for one second.