It's P2P, video, audio, codecs, and a whole slew of other things all bundled up together into the same "standard."
The P2P part is really really useful, but I could see some vendors wanting to break that off for various reasons. You can do that of course but... well... it's sort of like if "WiFi" referred to 802.11 + a bunch of video codecs + a routing standard + transport protocols + ...
If all you want is the data channel, then you can ignore the audio/video part, and just use the data channel separately. It doesn't do you any harm.
It does too many things. I want to use WebRTC data channels for a multiplayer game, but the current implementation libraries tie-in all the media components. It would be nice if there was a WebRTC implementation that provided data channels without having the media functionality.
Would you mind filing an issue at https://code.google.com/p/webrtc/issues/list to ask us to make a nicer build target? It won't be top priority, but we get around to it. Or better yet, if you get it working, send a patch. We'd probably include such a build target.