Do people 'tend not to go to' caffs? Which people? The Oak Cafe on Honor Oak Park, for example, seems to do quite a decent trade. My partner and myself are both quite fond of it. (It's probably fortunate that I find the smell of chips alluring on a woman...). And the neighbourhood as a whole manages to support four caffs within walking distance. Somebody's going to them!
Personally, I'm glad that Honor Oak Park is home to both the Oak Cafe and Hop Scotch. I use them both and they're both good at what they do. Although Hop Scotch could take a few tips from the Oak on getting the food to the table inside of an hour.
I take the point that it's good to have alcohol-free non-threatening spaces for anyone who doesn't feel comfortable hanging around a pub. And I don't have a beef with 'young professionals' per se. But browsing this forum, and it's East Dulwich equivalent, has made me aware of a little subset of the species who can sometimes seem a bit over-invested in the whole notion of being a 'young professional'. And I wonder whether coffee shops don't have a symbolic attraction for this subset that goes beyond pure utility?