Same with Google, Oracle, and basically every big company. In gaming, Valve is a holdout for now - maybe they felt burned after getting prosecuted for shoving Steam full of micro transaction gambling and they're laying low for a while.
Ok, but they bought DOS. They bought MSSQL (Sybase). They stole half of OS/2 and then pivoted to Windows NT with ex DEC folks. Its biggest products were all (mostly) bought. Oh yeah, Halo.