Smartwatches have only been around for a few years, but just like everything, what was once new is now old. The original Moto 360 and the Sony SmartWatch 3 are no longer being sold in the Google Store.
Their webpages are still active, but clearly state “no longer available for purchase”. The purchase button is also greyed out and only says “not available”.
However, Motorola has already released a 2nd gen Moto 360 a while ago, which consumers are more likely to purchase, and have a new Moto 360 Sport out too. It isn’t too much of a shock that the Google Store has stopped selling the 1st gen version. Sony, on the other hand, has not released a Sony SmartWatch 4 yet, but you can at least get the Sony SmartWatch 3 at other stores if you really want one.