I know http exposes get since it's such a frequently used method, in the words of the authors of Node: Up and Running, but I do not know why there is not a similar post method. I know post also must take a body but that seems trivial. So - why?
Isaacs doesn't even want the http module in Node's core, likely it was put there since it is so often used; but they figured you could do your own for anything else with http.request.
Also if they do POST then why not PUT and DELETE and etc. Likely they put in the get wrapper, and then thought there was no reason to keep doing that in the core. It is just there as a quick helper for the common GET request.
Node has the philosophy of "If it doesn't have to be in core, then it shouldn't" so, take that as you will.