You'll never get a real answer of why that specific route for the dates you are checking hasn't changed. It's possible it can change by the time I finish typing this. If you really want to get from Phoenix to Greece on any specific dates, if you find the price is within your budget/liking, go and book it. If you keep delaying, it may go up and make this trip out of your budget or more expensive. The great thing is, except for basic economy, if you buy the ticket now and then find a price reduction in the future, you can call AA to get them to give you a Trip Credit for the price difference for a future flight.