I appreciate your thoughtful response and I would also add that I have come across a couple of cases where adopted people were searching for biological family. I can conjure up a myriad of reasons why they might not want to make their tree public.
At the same time I do get a little miffed at having to deal with the 'no tree' or 'locked tree' matches. My matches are now in the hundreds (over the entire spectrum of relationships) and about one third are without public trees. I have contacted Ancestry several times to ask that they add another category to the filter so they can be sorted out from the ones where there is information to compare. I have not had a response.