It's more complete because Apple spent two years watching what others were doing with their watches and set about polishing things up. I'll most likely be getting an Apple watch myself but Apple were late to the game on this.
Other than the occasional Moto 360, I do not see many smartwatches in the wild (I travel a decent amount for work). Apple will be the marketshare leader on day 1. I fail to see how that equates to "late to the game".