Sure they "could" do without it, but it was to encourage use of the site (the more points you have, the more posts you can make). Keep Level 1s at low # of questions/answers they can post helped Yahoo (back in the day) limit the amount of activity 'bot and troll accounts could have, before they were able to get those accounts removed. Without a point system all users would be able to post an infinite number of questions/answers per day, from Day 1 (unless they programmed the site to limit user post based on the age of their account or the # of days the account was actively used, but that's not really a better method).
The point system is what it is. You're free to disregard the points if they mean nothing to you, but you will be limited by your account Level as to how many questions/answers you can post each day, and your account level is based on your account's points.