Microsoft still has soft power, but the benefit of the platform goes beyond just control. Consider that millions of people who wanted to play Valve's games had to buy a copy of Windows first.

If those people would have used their PC only for that game, yes. But that's not the case. People didn't have a PC just laying around thinking "oh crap now I need an OS".

On the other hand, if you didn't have a PC back in 1998 you bought one and Windows came with it. Or you already were advanced user, built one from components and installed Windows. Either legally or not, didn't matter much.

I understand that. Most people bought a PC with a bundled Windows license as a prerequisite to run the many applications they cared about. Those are still people who bought Windows, and some of the applications that justified their purchase were likely created by third-party developers like Valve.

I was trying to highlight one of the great benefits of owning a platform: your platform is made more valuable by the work of third-parties who build on it.