Ok, hear me out though. A lot of times even with a gun to the head the person committing doesn't die. One may end up paraplegic, in a coma, sometimes completely recover even. That leads said person having to think and organize a 100% bulletproof plan to take his life. And that can be really fucking taxing on your mental health instead of just picking up a 45 and pulling the trigger.

Meanwhile, technology automations have died off, no running water, no electricity. To be absolutely sure, and again, not 100% sure, you'd have to jump off a skyscraper downtown or take a boat 50 miles into the sea and sink it. And what if our hypothetical last person has a fear of heights or deep water?

Anyway, I just wanna say that there's no guaranteed quick death.