Death is just as pointless. Considering that you have all of eternity to be dead, it seems like a mistake to cut your brief life short, in case something changes in your perspective during the rest of it.
You don't "be dead", its not an active state, an ongoing experience.
You imply that the person would miss out and regret it, but they woudn't be missing out because they wouldn't be.
Suicidal people reading this and thinking I'm arguing in favour of it stop right there - I'm on a phone and can't write a full nuanced answer. But I think this is an important point which all the "permanent solution to a temporary problem" people don't really consider, and should, to see why its an inneffective exhirtation.