I personally don't think it is necisary unless you plan to breed or show.
I have 2 yorkies that both came with AKC papers, but I have not and will not register them. At 1st I thought about doing it just so they would be officially AKC. But the more I thought about it I realized I'd really only be sending the AKC money for them in turn to have my yorkie on file. I really don't need my yorkies on file with them, I'd rather save my money. I have their pedigree that the breeder gave me, and I have the form showing their parents name and litter # and I am fine with that.
They special to me with or with out the AKC having my money