In DotNetNuke 6.2 the Services Framework was based on ASP.Net MVC. During the development of 6.2 Microsoft announced they would be releasing WebAPI for ASP.Net. WebAPI is built from the ground up for the purpose of building services on HTTP. It quickly became obvious that WebAPI was a better approach to Services Framework than MVC. Since 6.2 was scheduled to release well before WebAPI, we made the hard choice to release an MVC based Services Framework, and then make the breaking change to WebAPI with the next major release.
To be clear, any services that were written for 6.2 will not work in 7. All existing services must be converted to work with the new Services Framework. The effort to convert a service is not great, This blog covers the process of converting Services Framework MVC to WebAPI.