Sony acquired tons of studios but it was (largely) in the distant past. I am making no moral judgements here, only seeking to provide a broader context.
(Defunct)
- Psygnosis -> Acquired in 1993 specifically as part of their push to have software ready for this newfangled "Playstation" -> Rebranded Studio Liverpool -> Shut down / Defunct in 2012. Had a 7 year multiplatform history (Various microcomputers, DOS, a bit of Sega).
- CyberLife games -> Acquired in 1997, rebranded SCE Cambridge -> Rebranded Guerilla Cambridge -> Shut down in 2017. CyberLife was a new studio that had shipped one game on PC/Mac prior to acquisition.
- Incognito Entertainment -> Acquired in 2002 -> Considered defunct by 2009. Only worked on PS games.
- Evolution Studios & Big Big Studios -> Acquired in 2007 -> Shut down in 2016 (Evolution) and 2012 (BigBig). Sony acted as a publisher in Europe on their first game then became exclusive publisher later on before acquisition.
- Zipper Interactive -> Acquired in 2006 -> Shut down in 2012. They worked together on several Socom games before the acquisition, but before that were known as a PC developer (notably on MechWarrior 3 and Crimson Skies).
(Active)
- MediaMolecule -> Acquired in 2010. Sony had them on lockdown from basically as soon as the studio started because they liked their LBP pitch.
- Guerilla Games -> Acquired in 2005. They had developed Shellshock Nam 67 for Eidos and Killzone for Sony - both companies wanted to acquire Guerilla, Sony was the winner.
- Sucker Punch -> Acquired in 2011. Started out for Nintendo 64, but then went Sony exclusive for a long time.
- Bend -> Acquired in 2000. They'd made one game with Sony that shipped the year earlier.
- Naughty Dog -> Acquired in 2001. They worked on several Crash Bandicoot games together prior to the acquisition, were multiplat prior to those games.
- Insomniac -> Acquired in 2019. Long history with Sony, but had switched to being a multiplatform developer before getting locked down.
Sony's most aggressive acquisition phase was the late 90's through mid 00's. It's true that many of these studios had a history with Sony - but this was also in an era when there were zillions of free, independent studios to commission large scale (for the time) games. When it took 12-18 months to make a whole top tier game. Sony and Microsoft were, in the early 00's, funding games all over the place for PS2 and Xbox.
Microsoft's content pipeline circa 2016 was dramatically smaller than Sony's. Both Sony had Microsoft had shut down several studios between 2012-2017, but Microsoft had fewer to begin. Microsoft's strategy going right back to 2001 was to commission lots of games from third parties - much in the way Sony was doing during the PS1 and PS2 eras before they started acquiring all their partners. Had Microsoft pursued the same strategy as Sony, we would have seen companies like Bioware, Bizarre Creations, Team Ninja and others become Microsoft studios.
By the mid 2010's, there were fewer such studios in existence at any meaningful scale. Most being bought up by publishers or going out of business, with said publishers being increasingly hesitant to go exclusive with their games on account of dramatically increasing development costs and increased ease of multi-platform development.
Thus, we have the modern industry context. Broad scale consolidation, massive studio sizes, a small number of massive publishers making fewer games than ever before with more staff than ever before.
