Version: (using KDE KDE 3.5.5) Installed from: SuSE RPMs It serves no purpose (I guess some kind of social-security :-) ) and it just disturbs the user -- user deliberately didn't chose "close" but "quit" and now she/he is asked if she/he _really_ want to quit. Choosing to start at login or not is even worse "feature" -- such thing should be established once for good in settings not each time somebody quits -- it is too easy to make a mistake and again, it is only a disturbance. I set status for wish, but in my opinion it is usability flaw (bug).
In trunk, the "automatically-startup-question" can remembered (the question will not be displayed anymore if the answer is checked to be remembered).
Related report: https://bugs.kde.org/show_bug.cgi?id=146423