Why? Because it doesn't reduce cognitive load. One seems to require at least as much brain space to code things in Angular, as you do just writing pure Javascript. That's a no-no, that means it's not a labor-saver long-term.
I use Scala because Google App Engine didn't support PHP for example. It's an Android app, so I use Kotlin for that.
I personally do not want to spend time re-writing my app every 6 months before it is even launched. I would much rather spend the time acquiring customers. I tend to choose a stack at least to start that I know I won't need to re-write in 6 months. Unless of course it needs to be re-written/refactored to accommodate all those customers knocking at my door ;)
That generally means I stay away from the front-end flavor of the week when starting a new app. Don't get me wrong, I myself have used Angular and Vue for a couple of projects but not in the beginning and not for the core product. I don't like the instability and constant changes of a lot of the newer frameworks.
During this same period, I launched 2 SaaS products on boring PHP 7 and Python for the backend and HTML, jQuery/intercooler.js for the front-end. Both profitable and growing.
I think sometimes devs don't realize the hardest parts of starting and growing a business have nothing to do with code or the tech stack you choose. Marketing, getting and retaining customers and everything else in between is way harder than writing code.