Outside of toxic work environment that would burn out anyone, one of the biggest reasons is going to be creative freedom. Under major established studios, a creative lead may have great ideas and wants to take risks on an upcoming project, but upper management that would prefer to show big numbers to shareholders will shoot down a lot of those great ideas and risks for something safer and so far away from the devs vision.
Gaming is nowhere near the same as it was 20 years ago where it was still considered a "nerdy" hobby to have, so major game companies focus now on reaching out to as many people as possible, and those big budgets are a big reason for it. 20 years ago, a AAA game could sell 1 million copies, and it would be more than enough to fund the next project. Now, those kinds of sales figures can shut a studio down. This is lowkey one of the reasons why I'm happy Astro Bot won GOTY.
When the behemoth that was Halo 3 released, Bungie barely had 100 developers that worked on the game. Compare that to something like Assassin's Creed Valhalla that routinely has thousands of developers. That requires a LOT of ROI to keep the studio rolling and so creative freedom is often very limited. Otherwise, companies will pull the plug.
One of my top 5 most anticipated games is Exodus from Archetype Entertainment. The Lead Designer and Lead Writer from BioWare's glory days starting with the first Baldur's Gate founded the studio and in the many Q&A videos they've posted about the game, they very often mention "creative freedom" being one of the driving factors behind the studios founding.
You called down the thunder, now reap the whirlwind
