If you are happy, no need to root. Android is plenty customizable without rooting for many folks. If you want to further customize your phone, it may be necessary.
I don't know what device you are running, but sometimes updates from the manufacturer / carrier are painfully slow. Sometimes with root and the courage to flash custom roms you are able to be months ahead of them with OS updates, or you would like a "pure" android device. Those are personal choices.