This life requires motivation, which requires goals. If you don't have anything that you think is worth achieving, then sooner or later suicide becomes the only reasonable course of action. If you don't have motivation you can't even get a minimum wage job, so unless you have parents that want to keep you alive you are also facing homelessness or at least poverty on top of the non-existent reasons to live.
Then there are the more mental-illness driven stuff like anxiety and BPD. Or just chronic physical pain, or a major life transition (divorce, covid, etc).
The toughest forms of suicidality to get rid of (ignoring end of life chronic pain) are probably the ones related to impaired motivation, and the more meta-level this impairment is--the more impossible it is to escape. Some kind of mixture between the final forms of depressive realism and a DNA that lost the fight against the neocortex.