Avatars are a great way to provide step-by-step instructions to resolve a problem. When you have a technical issue with your computer, sometimes it is just easier to listen to someone show and explain to you how to fix the problem.
Avatars are user-friendly and provide a more human approach to learn how to fix a problem. Some people learn by reading and others learn by watching and doing.
Naturally, this is not an "either or" solution. The tech support site would also provide written instructions. The avatar adds an additional method to resolve the problem.