Because Angular was the only real choice for awhile. That's like saying PHP is still bigger than you think because half the web runs on PHP but that is old legacy shit. Almost othing new and serious is using it.
[0] https://discuss.emberjs.com/t/why-is-ember-3x-5x-slower-on-a...
[1]https://eviltrout.com/2016/02/25/fixing-android-performance....