The PC market is extremely cut-throat. It has to be because consumers will go to great lengths to save a few bucks when buying their latest system. But it seems that this thriftiness hasn't resulted in hordes of users choosing to buy PCs without Windows installed and instead choosing to install Linux instead. In fact, there are plenty of users who would rather break the law and install pirated copies of Windows than go the legal route and install a Linux distro. On the whole, most people would rather spend the money on Windows (or Mac) than take the time to experiment with Linux.
1 — On the whole, users aren't all that dissatisfied with Windows
2 — Too many distros
3 — People want certainty that hardware and software will work
4 — As far as most people are concerned, the command line has gone the way of the dinosaur
5 — Linux is still too geeky
"Ignorance is the soil in which belief in miracles grows." -- Robert G. Ingersoll