Because writing code hasnt been the bottleneck for success on the app store in probably a decade, its all how to game algorithms / find someone with the power to boost your app
And the same is true for almost all those names the GP posted - they are big because of network effects - most people dont have time to evaluate the "quality" of software.
In the long term the "quality" of software can be extremely variable, so mostly people just hitch their wagons to existing tools because if everyone else is doing it, it must make sense.
