Then you haven't met enough people.

Not everyone has it in them to change. Hardships can force people to shape up or fall, and far too many will emerge from those experiences broken wrecks if they even emerge at all.

Then you haven't truly met enough people.

Has every single one of them changed? Not just superficially.

Then you don't know for sure that the rest can.

You're overestimating people.

Ah, but I know you are.

You don't. You just admitted that you haven't seen everyone you've met change. So you're only hoping they can. You don't know they can for sure.

On the other hand, I've seen plenty of people put in situations where they had to either change for the better, or perish. Unless you believe that so many would prefer to die instead of undergo change, I'd say it's quite clear that they just didn't have it in them.

They had help.

At some point, the world ceases to cater to someone. If there's no chance of the circumstances needed for them to change to come about, they may as well not be able to.

It's not assuming any given person won't. But not everyone can, either.

Then we'll agree to disagree. I can continue to be pleasantly surprised at times, and you will continue to be crushed under your optimism at others.