It has benefits
Yeah but then it would over-complicate everything. Idk if you play video games but if you did you would know that 3 OS systems is enough in the supported list. It would be an absolute nightmare to try and make game devs accommodate more operating systems. Having less operating systems is better imo. The issue with breaking up a monopoly is that it can make a company operate in a more complex manner. Look at internet providers as an example. I disagree with your point on operating systems, because this just makes it overwhelming for the customer. The three most common are Windows, macOS and Linux. Lets keep it that way.