Even the Universal Package Manager only solves part of the problem.
What I would like to see is a software installation process which correctly integrates the installed application with whatever desktop or user interface I happen to be running - so, for example, if I'm running KDE, it puts the application in the appropriate place in the applications menu, installs any needed configuration files, MIME types, icons, help files, etc. Same thing if I'm running GNOME, CDE, GNUStep, or whatever.
The fact is, that simply "building" the package isn't enough to make it usable to the novice user. And in many cases, even "installing" (in the sense of what RPM does) falls short of the mark.