Because being a Conservative has become too broad a descriptor. I agree that I am a Conservative libertarian or Goldwater Republican which is the same thing. That does not go against my assertion that I am a small "l" libertarian. I need to emphasize that, in order to separate myself from the War Hawk Neo-Cons who might be considered to be grouped in with Conservatives.
This is a contradiction in terms “Conservative libertarian”
conservatives are not liberals, you are a liberal that shares some positions with conservatives.