In my 25 years of using Macs, I have never had more than one user account.
Macs did not have separate user accounts until Mac OS X; which has been around for less than a decade.
There are all sorts of reasons for having a second user account:
-sometimes accounts get corrupted and you can't log in to them. Having a second user account can save your bacon if this happens.
-When an application starts to misbehave, trying it out in another user account will determine if the problem is system wide (i.e. the problem still occurs in the other account) or if it is specific to just one user account. If the latter, then it's usually a bad file in the user's home folder that is causing the problem. Many times I have heard about people reinstalling a misbehaving app or even the whole OS, only for the problem to not be fixed because it was a user account problem (which is far more common IME.)
-Having a second user account allows you to run your primary user account as a non-administrator. Apple recommends this for security reasons. Admin credentials should only be given to programs and tasks that need them. When running as admin, everything you do, every program you run, runs with elevated admin rights. This is an unnecessary security risk. Apple goes so far as to say to never browse the web or check e-mail while logged in to an admin account.
Let's say this did fix the problem, how would that help me? Can you delete a user account after creating it?
It would tell you that the problem lies with your user account, which would save you the trouble of reinstalling the whole OS, which many people do mistakenly. You could continue to look inside the user account for the problem. There are further troubleshooting steps that I can suggest.
