I'm not sure how underserved it is. I suspect that a lot of people just don't want to pay for a co-working space out of their own pockets and would normally content themselves with going to coffeeshops, etc. to get out of their apartments.
Added: And people can make do with situations for a limited length of time whether working from their kitchen table or suffering through a 90 minute commute that aren't necessarily sustainable long-term.