They naturally occur in markets with network externalities, which are quite common.
Of course industries like food service don't have monopolies, but they don't pay very well. They are also geographically restricted. I don't really care about those companies, they don't contribute much to the middle class.
Google is an effective monopoly, Amazon is certainly headed that way. Facebook is pretty close. Microsoft would be except the rare occurrence of someone writing a free operating system that was very good at the dawn of the internet age. Airlines are effective monopolies in their selective hubs. Monsanto certainly. They don't have to be the last company standing to show monopolistic tendencies in my mind. Microsoft wasn't technically a monopoly in the 90s, but it might as well have been.