Why wouldn't they? It keeps strengthening their position. It's an incredible source of soft power if they're seen as the place to look for good AI, and what's more, you can self-host it or hire a local provider if you're worried about data sovereignty.
‘Why wouldn’t anyone give away frontier AI?’ sounds like ‘why wouldn’t anyone give away uranium enrichment?’ i.e. I can’t comprehend the state of mind and the world model of anyone asking a question like that, which is apparently quite a few folks here on HN!
I guess it's a possibility, but I don't have that kind of expectations from major world powers. It's not like the CCP is a beacon of human rights either.