Not all businesses. I've worked for and with plenty of small businesses where the norm was OpenOffice, running on top of Linux and Mac OS X, with non-technical people having no problem using it (after a period of bitching about it, because people in general are conservative).
For example I helped a local kindergarten switch all their computers to Linux and OpenOffice (one in every classroom, plus 4 others used for administrative purposes). They are happy with the results and the BSA is not harassing them anymore. My wife works there and I'm happy to help out whenever problems occur and it's a lot better for me to SSH into those machines instead of going over there (and surely, you can also do that with Remote Desktop on Windows, but you don't have the same level of control and it's harder to secure, IMHO).
Granted, it's not always easy for a company to make that switch, because as I said people are pretty conservative and fear change. This is why developers are so fluid in regards to the technologies used, because developers know how to learn the basics and build from there instead of rote learning the path from A to B.
The one problem Linux does have in regards to businesses is integration with Exchange ... this is actually the deal breaker, as in Office coupled with Exchange is the real killer app, and there still isn't anything that can replace it for big organizations. But small businesses are better off going with services such as Google Apps nowadays.