you can fill one with your IDE
I don't. I have separate editor windows for each file, which I can tile how I like. I never understood why so many people bought into Microsoft/Apple's idea that you want a single program to dominate your monitor.
With widescreen monitors, it makes a lot more sense to have multiple files open side-by-side. Then, I even have room to spare for docs, command windows for doing builds & running tests, etc.
When I first started developing on Linux, there weren't really any IDEs for it. I guess there was Eclipse, but it was too heavy-weight and sluggish. Initially, I thought it was strange not to use an IDE. After a while, I got so used to
not using an IDE that I never want to go back.
I'll grant that IDEs are better for debugging, but more than 95% of the time I can do what I need by running
gdb from the commandline.
If you like IDEs, I'm happy for you. I just don't want people to think it's the
only way to be a productive developer.