Why people stays in a relationship that it's obviously going to end ?

Hi everyone, I don't wanna sound judging or hurt someone feeling, but why do u stay in a relationship if it's that obvious is bad, toxic, cheater, u are not happy etc.

Many ask here about a relationship advice but once I read there post,( like hallo i haven't dated anyone living in a homophopic country and feel that some gays don't know there worth, anyone who is just will take a littlebit of my happiness is out of my life) thinking why he is still with that person, why some may go blind and not notice the obvious that things must end?

I am sorry if I have a rude question, but I just wanna know. Is that how much some need to be in a relationship? Is it that complicated?