The financial model to subsidize a closed ecosystem is easier to conceive of than for an open ecosystem.
The closed ecosystem buys sticky users that are at the whim of the ecosystem's owner.
What the financier has to believe has fewer moving parts.
One-ply analysis is sufficient.
Open ecosystems have massive benefits, but largely as indirect effects.
What the financier has to believe has more moving parts.
At least a two-ply analysis is necessary.
Those are an order of magnitude harder to convince people of.