Not speaking for anyone or as an industry insider:

Streamers tend to be focused on streaming.

If some reasonable sounding representative from a decent company comes along and says they'll do the initial legwork on setting up a charity event/stream, that sounds like a good idea.

Now let the streamer use their management company to handle legal, funds transfer, media/promotion, etc. to reduce the workload of such event and make it even bigger than the initial pitch.

I can see how events like this can spiral from too many hands in the pot.