It's a symptom of browsers getting embedded PDF readers, which is a trend that was stared a while ago - long before Edge was a thing. Edge had to keep up with user expectations in this regard, so it also got one. But then, if you're already shipping a browser with the OS, and said browser has a PDF viewer, it's hard to justify also shipping (and supporting!) a separate app with the same functionality.
Re:Firefox 80
by wlesieutre on Tuesday August 25, 2020 @09:12PM
(#24278045)
Safari has displayed PDFs forever and yet Apple still ships Preview. It’s quite good in fact.
I only get them when the search box goes "You typed 'Snipping Tool' so you probably wanted to search for 'Snipping Tool' on Bing. Let me open that in Edge for you."
I did actually use IE as a frequent browser for a while when I had a Surface, on account of touch scroll/zoom being really bad in Firefox and Chrome at the time. But that was the only thing it had going for it.
EDIT: and as someone else points out, Edge's PDF viewer is now Chrome's PDF viewer and it's not as good