Why am I not allowed to die?

I've been experiencing suicidal ideation since I was 12, for the last 7 years I've wanted to die, despite numerous attempts I'm still alive but only because if I killed myself at the moment it would destroy my family. I don't want to live, I haven't for as long as I can remember but I feel trapped by them I can't kill myself but I have no energy or motivation for anything, nearly everything I do is out of an obligation to them and I'm so tired of it, it doesn't help they call me lazy, selfish and useless when just by not offing myself I'm doing more for them than they'll ever understand. Why can't they understand how I feel? I just want to die, that's all I want but they will never let me, I just feel so trapped by them and I can't help but start to resent them for it.