Do you think people with bad tempers have them because their life is harder or because their being lazy in self control?

Neither. It's usually because they're entitled narcissists.

Sometimes out of frustration and a feeling of helplessness.If you are self disciplined it helps to be able to manage it in public.

Short tempered people have a hard life.

Bad tempered people are personality disordered who want to control.

No, I think it heavily differs per person on what they experienced. Some people are just born with a bad temper others 'learn' to have that habit. There isn't 1 reasoning behind it, but I'm sure that traumas and bad experiences play a heavy role (E.G bullying). Anyone with a bad temper will have bad self control, otherwise they wouldn't have a bad temper.

It can be because their life is harder.

Bullying is number one.

Also it can be they are lazy in self control.