My worry is that only being available for viewing by purchase will discourage new fans from discovering it, thereby leading to Castle never being in demand enough to be offered on the streaming sites or showing back up in syndication. I don't think the average casual tv viewer is going to be willing to pay $25 for a season or even $2.99 for a single episode just to try out a show. Being part of a streaming service that is already being paid for would encourage more new viewers to give it a chance, thereby extending its potential post-cancellation revenue viability.