Because the term has a certain emotional impact. The purpose here isn't to be pedantic economists. The purpose is to sell something - in this case, sell an appr

Because the term has a certain emotional impact. The purpose here isn't to be pedantic economists. The purpose is to sell something - in this case, sell an approach to startups for how they can sell a vision to investors. "Monopoly" is a beautiful, meaningful word, not a technical specification. Investors don't hear dry economics. They hear "Potential for sustainable high profit margins in a large and hopefully growing market". If you want to get pedantic about Thiel, he argues that the monopoly does not need to be the direct source of revenue - in fact, it's better if it isn't. Consider Google. What's their monopoly? Search engines, which they dominate with their superior product. How much do they charge to use that product? Nothing. Google makes all of its income indirectly, off of ads served via their monopoly (and other monopolies they hold, like email).