It's not absurd that corporate entities would make changes to their software without a desire to release those changes as code. It has serious implications on patents etc...

If Blender had a stable C API that was dual licensed, you'd see a lot more studio uptake IMHO. Heck, even libc is dual licensed.

This all comes down to the GPL not being well received by most tech corporations. People can argue whether that's got merit or not. However it's a long standing fact that tech companies do not like having dependencies on GPL code that can "infect" their code base. Entertainment studios are the same. They're largely tech companies at their core that create art.