Dare I ask how having half a million terminals open in screen is useful in any way?
I guess it's a style of working. If you need to ask, that probably means you're not the kind of person who cares about the advanced tab-grouping features in firefox either, and you probably also never have so many different paper files open on your desk that you can't find space for your laptop? I'm not sure I can explain, and certainly not defend it - you might call it "organised chaos" :)
In any case, it's all state, and it doesn't all fit in your head. And a reboot wipes it out!
I wish I was that perfect! :)
I couldn't imagine being able to clean up stuff like that.