One solid reason would be to maximize its compatibility with other devices.
The idea is to be allowed to choose whichever brand and model of thermostat you like, whichever door lock you prefer, and so on. Having a smart home should not limit the controller to be available for select devices that will work with the system.
As is the case with Vera. You can use any device you want, from any brand. As far as the band of unique home control Devices continues to expand, this Vera strength will enable you to keep adding to your system.