Why is there a point system for answering questions?

To motivate you to ANSWER questions and choose best answers to your questions.

That is why you LOSE 5 points when you ASK a question. There is a limit to how many questions you can a answer each Yahoo "day." The Yahoo "day" does NOT end and start at midnight in YOUR time zone. Right now it ends and starts around 8 pm EDT on the east coast of the United States and 5 pm PDT on the west coast.

It's to encourage use of the site. You've already provided data by creating a Yahoo account, whether you ever use YA or not.

To encourage people to level up faster on this site.

To Encourage other people to Participate on Yahoo Answers

Yahoo Answers is used for Yahoo Seach Engine. To get people to answer questions they figured a point system with levels would motivate people to give answer questions. They use these questions and answers for their search engine.

It gives Yahoo a good feeling to have something they can take away from you without actually removing your account.

Because it helps you level up so you can ask and answer more questions.

To keep this site from getting spammed. You have to build up enough points by legitimately answering questions before you can do it unlimited. Chinese spammers use to flood this site and it was impossible to find real questions.