SSL: It is not the onus of the vendor to ensure people are properly securing requests. I have seen horrendous things done in the name of "security" but it only adds headaches. Fix this at the client level. SSL everywhere is sufficient. By extension, vendors often introduce mechanics because they want to make the world better: http://xkcd.com/927/
Platform Support: I think the counter-argument is community client libraries, which the OP is correct: they are worse. The stability + scaling + support issues mentioned by OP can usually be solved by better API design and better architecture behind the scene.
Backwards Compatibility: OP claims you never have to update your code if you use their client library. This is likely true. Good API design would dictate not breaking exposed endpoints unless there is new functionality to be had. In this case, to take advantage of any new API features, you'd still have to update your code. No cost savings are had either way.
