[nine_k]

Sometimes all you got is port 443, and adding subdomains is a non-zero hassle, especially if you serve all off the APIs from the same code anyway.

[eikenberry]

You don't need subdomains or other ports because you encapsulate everything in the protocol. A system that works on a protocol only really needs a data socket which can be simulated pretty easily via any URL with the POSTs working as a bursty stream.