I take great exception to this statement. Yes, I prefer to teach cave divers, deep wreck divers, and trimix divers a solo class. I charge them for the card, because they aren't likely to learn anything from me. Even if I did teach them, they aren't going to do it my way anyway, so there..
Full disclosure - Wookie was my solo instructor, and it was DEFINITELY worth it. I really enjoy solo diving, and with the card, I can do it at my local quarry without trouble (they give you a transponder and ask you to file a dive plan). Plus, I had such a good time solo diving in the Dry Tortugas off Wookie's boat, that I'm going back this year.
I think that there is a major disconnect about the definitions of solo diving and the social aspects of diving.
I am VERY much involved in the social aspects of diving. Almost all of my friends are divers, I'm the president of our local dive club and a member of two others. Almost every week we have some sort of social event. In the season, we have lots of group trips. I really enjoy the company of other divers - on the road, at the quarry, on the dive boat, and in the bar afterwards.
But I also like underwater macro photography. While I don't do this on every dive, one of my favorite types of dives is to just be on my own with my camera, looking for little critters. Without worrying about a buddy who is bored while I spend 30 minutes on one coral head. It's something that I really enjoy, and the solo card lets me do that in places where there might otherwise be a problem... Yes, if I have the wide angle lens, I need a buddy because I need a model. And if I'm diving in such a way that it's not appropriate (at my level) for solo diving, then I want a buddy. But I wouldn't imply (as some have) that there's a problem with someone who wants to dive alone...
To follow up on the other analogy, I ski too, and of course it's a lot of fun to go on a ski trip with someone. The car ride, the lift lines, the apres-ski bar - all very social situations. You know what isn't a social situation? Skiing! I mean, I find it annoying to try to match my pace with another skier, it's not like you are talking while you are skiing, I'm either having to hurry up or wait when I do have someone who wants to stick with me. I MUCH prefer to say "see you at the lift, have a good run".