...and it let's you manage them from the same place.
Why would I want to use different services? I (personally) use godaddy, my company uses namecheap.
Both seem to be doing fine and we check in on them once a year.
Different TLDs at different registrars, I guess. I don't see that feature relieving a big pain point either.
One irritation that has popped up for me is that I was unable to combine my domain names into one registrar. I managed to move most of them over to Namecheap, but they won't accept transfers with a .ws TLD, so that one remains at register.com. I suppose in theory I could move to Nuages and manage everything from one account, but something tells me I'd just end up using all 3 and my situation would be slightly worse off than it is now.