In life people would want to kill there self why when life is so important!?

It's hard to gain perspective when (maybe) you haven't been in their body. A lot of people find themselves scared of something bad to happen that will send them over the edge and they won't be able to control it. and sometimes it's the case that some people just don't think the world will ever get better. Believe me when i say this, life gets better, at the moment, it's really scary but life finds a way of giving you the will to move on from your dark mindset. Suicide is a choice where they feel death is the relief of all suffering because the path ahead is way to uncertain. It's one of the scariest feelings a human can have, the feeling of yourself telling you you can't be alive anymore.

Because they feel like life is not important because they have so much pain and anger and they are tired of supporting people or thoughts

They best answer is that some people are not happy and they just feel so empty in life!!

It's because they think their problems are bigger than they are AND they do not realize just exactly how strong and resilient they really are.