Bzzzt. 95% of cell phone buyers have no clue what a Debian apt repository is. They want an "app store". They probably don't even know what "app" is short for, but that's what they want.
they made the only choice they could make in the situation they were in. They'd proven they did not have the ability to develop a new OS and the entire eco-system around it from scratch. They found a partner who could help.