That's not quite how this works tho. Microsoft doesn't make games. Sony doesn't make games. The only exception is Nintendo but even they outsource a ton of devopment to studios like 1-up studios, monolith soft, retro studios etc. These companies just make a console that plays games and then they try to buy rights to good games or studios so they can make their games exclusive to that console to bolster sales. Sure, sony and microsoft could pour tons and tons and tons of money into creating their own studios i guess that make their own branded games but they have decided to focus on hardware sales instead. This is especially true for microsoft where the xbox is just a small part of the business where the PC market is their focus.

From a business standpoint, it makes 10000% more sense to just try and acquire other businesses that do the work under you and you just publish their games. Which is why nintendo, sony, and microsoft all try to do it so much. I mean Sony alone has bought 14 development studios since last year.