My reasoning is something that only I myself would know fully and nobody else really, and maybe SaSu would understand (even then, perhaps not even 100% comprehend it), but it's quite complex. For other people, especially IRL, they just won't "get it" and I don't have the fortitude, energy, or even wish to waste time to try to 'explain' only for them not to get it or dissect things. I would think my own reasoning is quite complex and there is NEVER just one reason or reason(s), even then the reason(s) is irrelevant to the fact that I would rather not play this game of life.
So to answer the question, (assuming IRL people) many people may assume that I did not thrive in life (those who know me somewhat well in life) such as being successful average adult whether in career, relationships, character, achievements, making an impact (though that is debated because the average person likely has the baseline, making ends meet, healthy relationships, general success in basic adult life tasks and day to day living, etc.). As for some people who know my character more, they would highlight 'mental disturbances, mental disorders, illnesses, etc.' which is quite insulting, but since I would not be around to experience the (wrong) presumptions, it wouldn't really impact or affect me. As for family, they would point to blame my weak character, failure to listen, and just general failure as an adult who was NEET for a good chunk of it, lacking many life skills that the average adult has, and only was able to make it to his 30's due to family providing basic needs and almost never living independently, having one's own place (barring while in studies - pre pandemic era), etc.
Of course, once I'm gone (have successfully CTB'd and no longer suffering), people IRL and even those who don't know, may try to 'fill in the (wrong) blanks' when it comes to reasons, causes, and what not, but it doesn't really matter to me as I would not be there to experience the aftermath, only that I have avoided many potential worse future fates. As someone who has been sentient for more than three decades, I already know and have a very good idea of what my life will be in the coming decades, and barring some major windfall (not necessarily just more money and/or financial independence before standard retirement age) I still would not wish to stick around.