1) Do you have every possible service listed in /etc/services running itself? If not, it's a straightforward logical jump that /etc/services doesn't actually control anything.

2) If you're using xinetd to control the service, there's no point starting the service manually. xinetd starts services itself in response to connections on ports, if you have configured it to do so.

3) By turning on the service manually, you're bypassing xinetd. If you're not having xinetd control the service, xinetd isn't relevant at all.

4) To stop the service from starting without xinetd, tell the system's rc system to not start it. How to do this depends on what your system actually is. What is it?

5) Turning on a service manually then wondering why it's running doesn't make a lot of sense, it started because you told it to.