The coffeeshop dilemma

There was an article on Gizmodo today explaining for the 1000th time why Windows 8 will fail and how Macs can take over on the desktop. I don't necessarily agree with all the points, but here's the quote that got me thinking:

Microsoft shouldn't just be concerned about the iPad and iPad mini. It should take note that Apple is now No. 1 in notebook sales in the U.S. The 13-inch MacBook Pro is consistently the top seller at retail, and all you need to do is peek inside any coffee shop to see a sea of MacBook Airs

Given that traffic stats still put Macs at 15% of the installed base in the US, why do you think that Starbucks and other coffee shops are close to 100% Macs?

There has to be some good explanation for this.