How come Android doesn't have a built in PDF viewer?

https://midwest.social/post/14629110

How come Android doesn't have a built in PDF viewer? - midwest.social

Forgive me for this stupid question. I just transitioned from iPhone to Pixel (GrapheneOS) and I’m curious why there isn’t a built in PDF viewer like on iPhone? It feels like you have to open things externally pretty often, but I figure there’s a reason for that. I haven’t used Android in many years and I recently developed an interest for the technical aspects of things, so again, do forgive this beginners question. Cheers y’all!

GrapheneOS actually has a built in PDF reader. Open the “Apps” app if it isn’t installed. Look for “PDF Reader” and make sure its installed.
I think I might be using the wrong terminology, forgive me. What I mean is, in my case, why does the PDF have to open in PDF reader instead of directly in the browser (like on iPhone)? That’s what I mean when I say “opening things externally.”

I think it’s a fundamental design question. Apple wants users to do everything within their ecosystem, so they internalize as many functions as possible, whereas Android was designed to be lightweight and modular. Everything you don’t absolutely need in a browser just clutters it up.

Personally I like the flexibility of using exactly the app I want for functions rather than having my OS enforce a default.