Same reason you’d want to live in this fucked up world full of injustice and suffering.
Most people have a very powerful inherent drive to survive, and a lot of people who think they’ve got nothing to live for experience a reprioritization and will fight like hell to survive.
Most individuals who try to kill themselves immediately regret their decision. This happens a lot with jumpers, where most survivors report immediately regretting the decision as soon as they are in free fall and their brains reprioritize survival over the petty or even significant reasons we had to jump in the first place.
Just after jumping and while mid-air, Ken said, “I realized, at that moment, this is the stupidest thing I could have done.”
“I instantly realized that everything in my life that I’d thought was unfixable was totally fixable — except for having just jumped.” Source