Well good to see you came around!
There are many reasons WRX/STi owners "don't" wave:
1. They didn't see you.
2. You didn't see them return the acknowledgement.
3. No time to react.
4. New owners and don't know 'the code'.
5. Are not subie enthusiasts.
6. Arrogant pr1cks.
There's many other reasons, but I hope you'll keep waving! I don't care about looking like an idiot when people don't respond because the ones that do respond put a smile on my face and make me feel like a million bucks!