Hmmm would you let M$ take control of fine tuning your PC for improvements? I wouldn't. They won't leave it purely at memory or driver or LAN performance optimisation. They'll be force-downloading and force-installing game updates you haven't agreed to, or beta versions of drivers, or even stopping you from installing game mods because they're not official products. Or perhaps stuff you didn't even expect, like the newly-released Adobe Acrobat auto-installing spyware extension for Chrome.
It'll end up being a case where Microsoft decides whether you can run a game based on what their interpretation of what your system performance is, compared to official game requirements. Remember the old days, when we had to scrabble around for your DOS floppy boot-menu disk just to scratch out an extra couple of Kb of RAM to run something? We'll end up needing different OS versions - one data-hoover for MS and one non-MS (or non-Win 10) that you can use for games.
Microsoft aren't doing this for any other reason that they can see, somewhere, an opportunity to exploit either your wallet or your data.
I have Windows 10 on my not-for-gaming laptop, as does the wife, and the machine I built for my kids. My gaming rig won't get a sniff of Windows 10. Ever.