[fmavituna]

There are couple of reasons, one stated in the article, but second is a little bit more subtle, only advanced users will buy Mac and then install Windows on it. Those users generally don't execute everything they see on the web, free or crapware etc.

Another one from the article: "A main factor in this machine's metrics is the fact that every Windows installation on it is clean. With PC manufacturers loading so much crapware on new laptops, this is a bit of an unfair competition. But, on the other hand, PC makers should look at this data and aspire to ship PCs that perform just as well as a cleanly installed MacBook Pro."