Great attitute! You really need that kind of thought process or bowhunting will eventually drive you bonkers. There are a couple of possibilities. ONe is that you are not high enough. Another is that your tree does not have enough cover behind it. When picking a tree you have to look from a deer's perspective. If you look up at the tree and there is nothing behind you but the sky, you are in real trouble. Especially when you are talking about mature bucks that have been around long enough to know what that blob in the tree is.