The Caribbean side of Panama attracts a type of tourist few other places see: seafaring backpackers. That there pic of the West Holandes anchorage in Panama's San Blas islands, is a view of several vessels that serve this subset of the adventure travel community. In fact, The Fox was the only boat in this view, that was not a backpacker boat.
From what we saw during our time in the San Blas, the typical seagoing backpacker is an adventurous 20-to-30-something, single, white, and middle class. They're seeing Latin America on the cheap and want to experience the Spanish Colonial city of Cartagena and see a bit of Eastern Panama, one of the world's last non-industrialized areas. In Eastern Panama, the through-roads on shore - hence, the buses and other land-based public transportation - peter out a few miles SE of Portobelo, Panama. The only reasonable way to get from Panama to Colombia in this roadless area is by plane ($$$) or charter boat ($$). If these young adventurers can make it as far as either Panama City or Cartagena, the backpacker boats are waiting to take them the rest of the way.