Yes. You can use libraries when the service you're trying to interact with works according to some standard.

An example: I have an app I wrote at work that is a JavaScript frontend powered by a REST API backend. The REST API tries to be a good REST citizen: proper HTTP implementation (201 + Location when something is created, 202 for "I will get to that eventually", etc.), consistent URL conventions, and a consistent data format.

The end result is an API that is easy for humans to understand, but also easy for computers to understand: the simple CRUD code was about 10 lines of backbone.js, because my API doesn't break any conventions. This means that the code to interact with it already exists, and all I had to do was make the web page look pretty.

This is a good use of programmer resources, now and in the future. In the present, I didn't have to do any work to make a pretty GUI. In the future, someone that wants to pull data from my API will not have to swear at me -- everything you can do is easily discoverable by starting from the root resource.