Prior to Homekit based compatible product launched a month before, Apple are now stop selling Nest based product from online and retail stores. The Nest Learning Thermostat and the Nest Smoke Alarm will be no longer available since it gave direct competition to Ecobee3.
It is normal for Apple to give a favor to third party vendor who follow their standards. It is to ensure all third party devices are compatible with future Apple’s ecosystem. Previously, Fitbit activity tracking device have been pull of the stores to give a away to Apple Watch.