I *am* running outdated software because of one or more of the following reasons, roughly in the order of magnitude:
• Newer versions tend to depend on half the GNOME stack, or have Linuxisms making porting harder, or have much more insane dependencies than the predecessors (autoconf > 2.62 needs GNU m4, 2.62 could barely be patched), or something like that, or need Poettering crap
• Newer versions don’t work (as well) in compat_linux of the BSDs
• Interface changes (including loss of features)
• Newer versions use GPLv3 (or are otherwise less free)
For example, Opera 9.27 because newer 9.x versions don’t work on compat_linux as all, crash more often, or have those interface changes even though they occasionally may work on BSD. (My main browser is still Lynx though.) And indeed, Mozilla is at its end at the “old” company desktop too – recent versions refuse to start on Kubuntu 8.04… and I dislike KDE 4 a lot, and the “new” company desktop has Unity which is even worse.