Edit:
I'm speaking from the perspective of an upper 20something. I'm part of a generation that jumps jobs when the opportunity is better, or just because "it's been too long", not the one of years past where I'd be expected to work my way through the same company my entire life. With that said: if my new job says "we use Slack" then I use Slack, end of story. If they say "we use IRC" then I'd Google for how to use IRC because I have never ever used it in my entire life, never read up anything about it in my entire life, and I definitely don't hold IRC in high reverence like many posters here do. All I can see when I google IRC is that it looks ugly and honestly, that's what's most important to me these days because I have to look at, and interact with, the thing for 8+ hours a day so the least it could do is work out of the box, look modern, and doesn't need me to waste hours fussing with some dotfiles to get it to look the way I want, which is exactly how most modern chatting apps look (again: to me it's a waste of time, when I can just grab a off the shelf solution).
I appreciate that there is open source, and that there are free programs out there. I appreciate all the libraries that make my life easier. But the thing is, these are all tools I use to do a job. I don't care at all about the history of say gcc. All I care is that it works and compiles my programs, and if it does, then so be it. And if it doesn't? There are other options, icc, llvm, etc. My point is that at the end of the day, all I want is a tool to achieve a solution, and who makes that tool, or the history behind that tool, doesn't matter to me at all. It's not even part of the equation.
When the "new" tool is worse than the "old" tool, i care (and yes, the "new" tool can be worse - and often is - yet displace the "old" one, not because of its quality, but because of external reasons - like the developers of the "old" tool being unable to sustain its development).
Have you done a full migration of a grown Wordpress blog to another system, without breaking stuff? It's not something you do on a weekend or two. Changing away from a tool that holds lots of data and configuration is expensive.
Proprietary software that is years past its support date, from a company that has not existed in years, yet still in use, is also a thing.
The one kind of entity that dies instantly when its backing goes away is a proprietary website.
