It sure is useful. If you create an account then all your contacts, messages and games will be saved so if you need to reset and wipe your phone or buy another one, then as soon as you enter the account details all your information will automatically download again
I think you are confusing with a Microsoft account. He is asking about a Nokia account which is really only useful for some Nokia apps. I don't ever really use it.
My apology as I misread it. Hope you have your situation resolved for you *smiles*