Or, they've had System Administrators doing it for them their whole career and have no real clue what's involved anyway.
There's certainly multiple levels of comfort with software installation in this environment. Many of our good programmers get frustrated and end up asking systems to install programs or work almost entirely on their OSX laptop. Personally I don't find it too limiting because I am comfortable installing in my home directory.
The fact that sysadmins do often have that responsibility, though, means that sometimes programmers have less incentive to learn it themselves.
It's a mix of laziness and doesn't want to know more outside VB/C#. It's for an excuse to get a coffee break, a smoke break, or something else.