Hacker News has a pretty cool archive feature. I'm certain if you go back about a decade you'd see a similar response on anything regarding Internet Explorer. It was the most dominant browser, by a wide margin, even when there were browsers many felt had long since improved beyond Internet Explorer. And those alternatives came from companies that didn't have the reputational issues of Microsoft, somewhat ironically Google was one of them.
Yet today it's become the same thing with Google. They had a phenomenal search engine, but it's gradually gotten worse while other engines have taken some big strides forward. Its marketshare is just completely out of wack with its capability, and so I think that motivates people pretty strongly since it indicates a knowledge gap in the market. This is also a pretty new thing which further adds motivation - a few years ago Google search was, without doubt, king. Now, it's not. And, again similar to Microsoft, Google is increasingly destroying its reputation so it feels good to swap, let alone when other services are now also arguably superior!
To see some degree of evidence of this look at posts related to Google, but not their search. Posted just today (so there's going to be a large overlap in users) was this [1] post where a sunken car (found to contain a corpse) was visible via Google Maps. Nobody decrying Google Maps because it's still the clearly best service for satellite/street imagery. Gotta give the devil his due.
https://news.ycombinator.com/item?id=20954545