My two cents are the opposite view:
I doubt there is a successful company using vim or notepad to create html.
My observation is that nobody is using WYSIWIG HTML editors. Never seen it done anywhere.
They were however using text editors like Sublime Text, Atom, vim, emacs.
As for successful companies I think you will find they especially don't use WYSIWIG tools. In fact they have so much dynamically generated content it would make little sense. Google has Angular, Facebook has React, Yahoo has YUI, no idea about Amazon, ebay and so on but you get the idea.
WYSIWYG may have it's place for throwing up a ton of static content. But even there people are using blogging packages and so on.
OK for hobbyists, but in the real world, not so much.
I have dealt with the "real world" above. As for hobbyists, well, a hobbyist working on a Pi would be well served by vim or some such text editor. The Pi is not as fast as a PC or Mac and has a lot less memory.
So who does use things like seamonkey?
Memory in C++ is a leaky abstraction .