[makmanalp]

Because the de-facto transport for it is HTTP, which a) People know b) Is simple and predictable c) Has had support from every language on the face of the earth, for ages and thus d) Takes 1 minute to get up and running with, as opposed to, say, SOAP etc. e) Fits the CRUD model fairly nicely, which comprises the majority of web apps.

Nothing to do with one man's phd thesis or anything (that came YEARS after he wrote the HTTP spec and after most RPC systems). If I had a penny for all the theses that proposed something reasonable which was ignored.

[josephlord]

You missed: gets through proxies and firewalls.

Unless that is what you mean by (b).