It's not just about being physically able to install something (i.e. having admin privileges), we aren't allowed to install (or even write) anything that is "network aware" for security reasons.
Most average employees just need to get their work done, so they are not going to risk a fight with the IT machine over a browser. To non-geeks, it's just an annoyance, not a major blocker. Better for them to save their energy for a fight that matters (like getting an exception to the 100 megabyte email quota).