Apple has often been criticized for the lack of choice in the iPhone models, other than the generation of the iPhones and the internal specifications like the amount memory. Every one of the more than 500 million iPhone users have one of the three or four generations (mostly) of the iPhones and there is no way to choose an iPhone based on your personal choice of design, other than color and more recently on the screen size. But still no two iPhones out there look alike, even if they are the same model, and this is because most of the iPhone users have a protective case on their iPhones and Apple has been happy to cede this space of customization to third party case makers.
The scenario with the most recently announced Apple Watch, though is very different. There are two sizes of the Apple Watch, then there are different models, like the Sport, the Regular (?) and the Edition, then there are a bunch of straps with different colors and designs, the Apple Watch itself can be chosen from a few colors (and not to mention the different watch faces that can be chosen as the display, that make the total number of permutations and combinations to choose from, more than two million). So clearly Apple's strategy on the Watch is very different compared to the iPhone and this is a deliberate move. Apple has been very vocal about touting the Apple Watch as the most personal devices Apple has made till date and when a device is this personal, people should have a lot of options to choose from. Moreover the iPhones spend most of their times inside the pockets, whereas the Apple Watch is going to be on display on your wrist for everyone to see. So the fashion component of the Watch also demands a lot of choices to available in the first place.