Alexanders, I guess the correct question should be: why do YOU get to decide what might be a "good" match? We both paid the same amount of money, you see mine, but I don't get to see yours. I wonder if you would keep a private dna tree if you could not see anyone else's tree? In other words, if all of our public dna trees were closed to you because you kept yours private, what good would your dna results be to you? Not much, right? Because you would have no information from us to decide what is a "good" match. It's a one way street. That is why so many object to Ancestry sharing our information with those who choose not to share theirs.
Still curious why you would choose not to have a barebones tree with no personal info or documents on it, especially when it would even up who gets to decide if there might be a "good" match.