It’s a good question. SFGate’s Mark Morford give it some ink:

My SO, she is not alone. This exact same scenario, with only slight variation, is happening throughout the nation, right now. Are you using a PC? You probably have spyware. The McAfee site claims a whopping 91 percent of PCs are infected. As every Windows user knows, PCs are ever waging a losing battle with a stunningly vicious array of malware and worms and viruses, all aimed at exploiting one of about ten thousand security flaws and holes in Microsoft Windows. Here, then, is my big obvious question: Why the hell do people put up with this? Why is there not some massive revolt, some huge insurrection against Microsoft? Why is there not a huge contingent of furious users stomping up to Seattle with torches and scythes and crowbars, demanding the Windows Frankenstein monster be sacrificed at the altar of decent functionality and an elegant user interface?

Excellent question. Why do most people just put up with this crap? The answer may be in a quote I heard years ago, attribution unrecalled: the greatest damage Microsoft has done to the computing industry is the degree to which they’ve lowered people’s expectations. They’re a marketing machine, not a real tech company, and it shows in both their market share and their product quality.