Why is it that makes people so keen on answering sucide questions ?

Not really, I think by reaching out to people the person actually shows hesitation, and that's why people answer to "help". If he's actually serious, he won't be asking here in the first place. Sometimes all you need is a bit of company, and suicide is no joke. Sucks if it's a troll, but it is in all seriousness not a joke. If someone said he had the thought of suicide, the probability is there, and sometimes people do it in a clouded judgment.

Some of them are keen on helping with their advises, others positively enjoy other peoples sufferings, to me these questions are absurd and I don't think they should be answered in any way...

I imagine most people feel the need to try and 'save' someone.

Unfortunately though, most of those questions are troll questions.

most aren't serious and just want attention for some sad reason

Someone has to tell them that they're not failures and that they can succeed in their attempt if they tried.

because every on against the sucide question.