Why do you get negative points for asking a question ?

Several reasons:

(1) It's to prevent spammers from getting a new account and then asking questions up to their limit. By limiting the number of questions they can ask as a new member plus deleting points, the spammer is prevented from just spamming the heck out of us.

(2) It's easier to ask questions than to answer well so it encourages you to answer other people's questions in order to have enough points to ask your own.

(3) It encourages people to ask questions that matter to them since it's going to cost them points. If we didn't have to pay for questions, some people would ask a bunch of silly or nonsense questions. (People still do ask silly and nonsense questions but at least they can't ask a ton of them without having to answer some in return.)

(4) Yahoo gives you 3 points back when you choose the "best answer" to your question so this feature will encourage you to actually choose someone and not let the question go into voting.

You lose 5 points for asking a question cause that's just the way it is!

The reason is because they are trying to get people to do more answering of other people's questions in the hopes of trying to help someone out.