However, he usually did have justification for most those programs. Writing code on one project, examining specs on word and excel formats, surfing in MSDN etc. Having his machine automatically "garbage collect" those apps would've meant that he'd been wasting half of his time waiting for those big project files load(WAY more than 5 seconds, no matter what the author of the article claims), or try to re-find the helpful web page he had had open five minutes ago.
The way I imagine it working, the system would only garbage collect programs that had no open windows. Having windows in the background mysteriously vanish because they haven't been activated in x minutes is far more user-hostile than having a "Quit" menu item!