If we get docked five points for asking a question...?

The major reason that yahoo have the limits on the lower levels is to prevent malicious users from flooding the site with their posts. These include spammers and other advertisers (there are even auto-posting bots that do it), trolls, and other abusers.

It also helps new users to take it slow and "learn the ropes" as they progress up the levels. And helps new users to understand how YA is supposed to work. Also it encourages the user to answer/vote more questions and earn points.

People get entertained by the various answers. There's amusement value. Besides, people only get docked 2 points per question if they choose a "best answer" before the time for answering expires.

Yes, Yahoo takes 5 points when you ask but they give you 3 points back when you choose "best answer" instead of letting the question go into voting.

My feeling is that if it's not worth 2 points to the asker to ask then it's not worth my time to answer.

You earn back three points once you choose a Best Answer for the question that you asked. Then you answer a question [ it's called Yahoo Answers, after all :) ] and earn 2 points. Now your point balance is right back where it started.

It's to encourage participation in both asking and answering.

that is the roles and you must follow them