Why is it that websites find my gender so important? Are some results or options disabled or enabled for a certain gender or something?

I doubt it.

But seriously, why is it important at all for anyone to know? I mean, imagine if the sites were asking what race you were? what religion? I'm sure there would be much more objections to those. So why is it ok for them to ask me my gender? =_=

Age I understand. Websites don't want underage groups to have access to certain things (although really if a brat wanted on to something they'd just lie anyway)

But where I live? my Zip code? My Gender?? That is none of their business.