There's no realistic competition because the amount of work to switch your OS ecosystem, especially for businesses, is huge. So the product doesn't have to be good, you can just slam ads in the Start menu or whatever.

At one point the product is getting so bad that the cost of switching becomes a real consideration. It seems that every other year I hear about businesses and governments making the move.

The business version of Windows doesn't have ads in the start menu. That's the consumer/home version. The "Pro" flavors of Windows are quite a bit more pleasant and I don't think there is any downside even on a home computer.