The fate of non-desktop-environment applications

I've seen claims in the same ballpark made before, and they always make me confused. Do people actually restrict their applications to whatever is in their current desktop environment? Otherwise, I don't understand how this could possibly work, and without working perfectly, I believe such a feature would only create confusion and irritation ("Why am I still getting messages in this one application when I told the system I didn't want to be disturbed?").

Just to provide a concrete example, I run a KDE4 desktop, with KMail (KDE) for e-mail, Psi (Qt, but not KDE) for IM, Opera (their own toolkit) as my browser and RSS reader, GnuCash (GTK+, not sure if it integrates with GNOME) for accounting, Weechat (ncurses in screen in a Konsole terminal) for IRC, Emacs with Gnus (GTK+ or terminal) for usenet news and, for what I believe is the largest part of my communications load, Emacs with LysKOM (again, GTK+ or terminal, and no, you're not expected to have heard of LysKOM). And suppressing incoming messages is just one tiny part of the problem: What's the point of adding Nepomuk metadata to my documents if Emacs in LaTeX mode can't use it? Why have Akonadi store some PIM data, when it can't see the equally important data in RSS or usenet feeds?

It's taken a number of years of testing lots of alternatives to come up with this mix of applications, and while I'm always looking for better options, this seems to be the current local optimum for me. But do "normal" people stick with whatever KDE or GNOME gives them? Do desktop environment developers therefore ignore people like me?