My cross bike serves three purposes:
1. I race cross on it when the road season ends
2. I put on a beater wheelset, bottle cages and fenders when not racing cross and it's my winter/bad weather training bike
3. I commute on it because I don't mind locking it up outside and MTB pedals/shoes make a lot more sense
If I didn't race cross, I'd probably wouldn't use a cross bike for 2 and 3 above. Cross bikes tend to have a higher center of gravity, a slack geometry, less bar drop from the saddle, tend to be heavy and canti's don't stop you as well as regular road calipers (well, unless they are super expensive ones like Paul's or something, but then I would feel bad about leaving it outside.) I'd likely build up a real cheap road bike that could fit fenders over a cross bike for roles 2 and 3 above.
That being said, the more people pedaling a bike the better...and if the bike happens to be a cross bike, the more likely there will be a new cross racer and more chance to get information about this great sport out there. The only downside from selling cross bikes as general purpose bikes is the lack of race-specific models on the low/mid price level. But since I like the fact that my cross bike is multi-purpose, I don't mind that. Some others seem to care though.