Most corporate environments don't allow you to install software that isn't authorized. As developers we're normally given full administrative control over our systems but that's not the norm in most moderate to large companies.
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).