Outgoing Microsoft CEO Steve Ballmer has revealed in an interview with ZDNet that the company felt forced to manufacture its own Surface line of tablets to better compete against the iPad. Ballmer also said that the company’s decision to make its own hardware gave it the best shot to keep pace in a computer landscape where smartphones and tablets are evolving into the dominant species, even though that meant antagonizing some of its OEM partners that also make Windows-based computers.

Ballmer admitted that “nobody ever buys Windows” adding that “they buy Windows PCs” — a surprising statement from the CEO of a company that made its billions over the years mostly through software sales including the Windows OS family and the Office productivity suite.

The CEO admitted that “one of the things tech companies really do terribly is build new capability” while touting Microsoft’s ability to adapt when the market requests new products.

“We’ve had to do it a couple of times, in fact, from platforms to apps, from now software to services, from OS (operating system) royalties, to OS royalties and devices,” Ballmer said, although the company certainly took its time coming up with competing products, especially in the mobile business, and had failures under its belt in trying to compete with iOS and Android smartphones and tablets.

Ballmer said that the Surface initiative was “a tougher bet” than the decision to build the Xbox, which is itself a popular and iconic product for the company even though some analysts keep asking Microsoft to spin it off because it’s unprofitable. But it was a bet that Ballmer said had to be made, as Microsoft “had areas of vulnerability in competing with Apple” especially at the high-end of the device market where OEMs were not investing enough.

According to Ballmer, the Surface tablets are “tools that make people more productive, IT people, developers and end users,” but at the same time Microsoft’s software should also help people have “serious fun.” Whether Windows 8 users have fun or not using their devices, the new Surface 2 and Surface Pro 2 seem to be selling like hot cakes in stores according to a recent report and it looks as though the company’s push into the mobile world is starting to pay off with the rise of Windows Phone.