It might be a little glib, but that’s the main incentive I see here, especially since they’re exclusively using their own system, Github Sponsors, to direct the money. It makes sense, but if it was truly only about the maintainers, wouldn’t it be better to get the money to them through whatever means they choose to implement?

But you’re right: in the end trying to find out what their actual motives are is purely speculation, and I shouldn’t have phrased it as if it were a fact.