Why did Microsoft do it?

I didn't say it was impossible. As of 5 minutes ago, if you go to HP's website, they have 76 desktop choices. 9 come with W7, and 67 come with W8. There are 76 laptop choices. 16 come with W7, and 60 come with W8. Perhaps most interesting, if you click on "high performance" desktops, there are 8 choices. 7 of them come with W8.

Dell is about the same.  99 desktop choices, 17 with W7 and 72 with W8.  76 laptop choices, 19 with W7 and 57 with W8.

Based on this quick glance at what the top 2 PC makers are selling, it looks like 80% of new PCs and laptops are shipping with W8.  As it relates to getting a PC or laptop with W7, perhaps instead of "not easy to do", I should have said "substantially limits your choices and options".