One Ruling System
The goal to all of this is of course that one closed system controls your life. Be it OK Google, Hey Alexa, Bixby, or Siri, the first design criteria is non-compatibility. The consumer MUST not be given the choice of the best individual product -- they may ONLY buy those that are compatible with their system.
A generation ago there were "minicomputers", with the thousand pound gorilla being Digital Equipment. When they came out with what would be their final system, even the paper for the printer had to be purchased from them. IBM, who had been frozen out of that step in computers, left the system relatively open, even letting Microsoft do their version of the operating system.
IBM and the rest of the "Personal Computer" crowd won, Digital went out of business.