It looks like Nintendo worked very closely with Apple as of lately. In addition to the introduction of a first-party Super Mario Game for the iPhone. Niantic was just as busy with Apple in bringing the number 1 game of the year to a playable format, right on your wrist.
A demo was given with the Apple Watch, showing what the interface looks like when you go for a stroll searching for Pokemon or Pokestops, both of which are fully supported on the Apple Watch now.
You can add complications to your Apple Watch face to see the progress of your eggs. It looks like you need to “start a walk” in order to play the game. Once started, you will see the familiar view of “nearby” Pokemon. When reaching a Pokestop, you’ll get a ping on your wrist. Then you can swipe and collect items, just like on the full version.
You will also be able to collect medals and the distance you walk will count toward hatching your eggs. It becomes a really nice Pokémon Go companion app. Once finished, you end your walk on the watch, and the summary will show you the amount of steps walked, distance, and items collected from Poke Stops.
Niantic Labs CEO John Hanke was at the Apple event, and also tipped that the Pokemon Go Plus accessory will be available “this month”.
Why would any developers spend their resources to create an app for a platform that only have a miniscule number of user?
its all $$$$
it also depends on Microsoft if they want it on their devices, not just Niantic and Nintendo