One trivial reason might be the size of the artefacts / hardware requirements? Kimi K3 is ≈ 1.5 TB and requires multi million dollar hardware to run. Compared to e.g game development, I'm guessing that it's not like a bunch of people at Anthropic/OpenAI have the models running "locally".

It's easier to protect a power substation from being stolen then a Rolex watch