They are, however, generally combined so that an ATC controlling CTA (remember that one?) also has the Class G frequencies merged.
Which is the problem the present system has created by expecting one ATC to provide services to all classes of airspace. If the Area VHF was kept separate from the dedicated control frequencies, then there would be no over transmitting of the "control" comms by "uncontrolled" comms. It's probably just the push of a button to uncombine, but it makes more work to listen to it like that.
Putting my grandpa hat on, I remember many years ago having an ATC sit in on my FS console for a famil, and him being amazed at all the radio chatter on the Area Freq. "How do you put up with that for a whole shift?"