Microsoft are quite simply the only real option for 90% of computer users.

This is because to communicate with all those others in that 90% you need Microsoft products.
You could say, look at the state of the roads I dont think I should use them any more. But try getting anywhere without them.

All the open source products allow you to save in Microaft compatible formats, Why? so the documents can be read by people who use the 90% of Microsoft software. Not ideal but the way it is.