That's pretty interesting if true. It must be because you're the only one still doing it. Using techniques just for your idiosyncratic inbox doesn't make sense to a spammer. But if every inbox was only doing this, then your experience would be much different. Nothing but unstoppable spam. Exposure = money. Why would they not spam you? They don't like money?
As I've said, I'm not interested in theoretical arguments. All of my domains wildcard forward to the same email address, too. Filtering client-side has never been a problem.