Why do they always use dying to guilt trip?

I recall ever since I was very young, my mom would always say she is depressed and wants to kill herself, that she regrets having kids because she is broke thanks to us (and not her own poor financial planning).

I remember I was always so scared I would come home from school to find my mom dead.

Now that I’ve become an adult, she is going insane that I refuse to let myself be manipulated by her anymore. During one of our arguments she asked me why I’m so heartless, and if I would even appear at the funeral if she died.

And a few moments later she said she’s just concerned for my mental health, that there’s something abnormal with me because I don’t want to have a relationship with my parents, that she’s afraid for my mental health after she dies.

I wanted to tell her that I think my mental health would actually improve if that really happened but I didn’t, because she’ll just use it against me to say I’m heartless.

I’m so tired of them bringing up them dying all the time. I actually think they will outlive me. I’m literally so used to her script that I don’t feel anything when she says these things anymore. I guess it’s all she has left in her handbook of manipulation tactics.