I don't think anyone is arguing that if Microsoft blinked out of existence, no one would be inconvenienced. What a lot of people ARE saying is that "if not Microsoft, someone else."

If Microsoft never bought the software that eventually turned out to be Office, someone else would have provided a solution. If Microsoft hadn't bought (and resold) QDOS, someone else would have provided an operating system for IBM, and people who make chairs wouldn't have seen a big difference today.