In the original days of iPhone, you could really only use it if you had a computer (to sync through iTunes, and to activate it if you didn't buy it in the store

In the original days of iPhone, you could really only use it if you had a computer (to sync through iTunes, and to activate it if you didn't buy it in the store). iCloud got rid of all of that. I don't see why Apple wouldn't do similar with the Watch, especially since more of their services (Messages, Health) are being moved into iCloud services in iOS 11/watchOS 4.