I always wonder why, out of all the mobile products, is the Apple Watch the only one not called the iWatch? iPod, iMac, iPhone, iPad ... Apple Watch? Feels like somewhere along the line they decided that naming all their products something with the letter 'i' was silly and dropped it.
My guess - the 'I' prefix was tied to the Digital Hub initiative, where software and devices would tie in via your home computer to share music, home movies, photos, etc.
When it became clear that the cloud would replace having all of that maintained on a home computer for most people, adding 'i' as a prefix ended - with iCloud.