It seems that neither Apple nor Facebook is particularly attentive to the developers who build on their platforms once the app is released. Curious models for companies whose success is largely due to the developer community.
I don't know about Apple, but I don't think that Facebook's success is due to the developer community. I would argue that the arrow of causation is reversed in Facebook's case - developers are interested in Facebook because of its market share, rather than the reverse.
Apple and Facebook don't get success from having lots of developers, they get success cause their users get access to some cool apps. If they burn X% of developers, then that's OK. Lots of their users don't complain about apps they never saw.
It is a matter of scale to a large degree - supporting so many developers efficiently, while still preventing harmful abuse.
They both could improve in many ways, for sure, and given the contributions developers are making.