Ghost Gates :-)

For the last few months, I have been flying around the world,visiting every continent. One thing that has been baffling me is that at some smaller airports, and I do mean small, I see gates at the terminals, yet at some major airports, there are no gates at all.Today, I did some experimenting. I usually have autogen at Dense to Very Dense. As I was sitting at the terminal in Sydney, wondering why there were no gates, I pushed the autogen to Extremely Dense, and VIOLA!!! gates appeared.Now here is the mystery. I then moved autogen back to Dense, and the gates were still there. So my question is, why? If they show at Dense after setting to Extreme, why wouldnt they show at Dense in the first place? Anyone have an answer?