I don't think that's a good explanation at all. People are murdering less than a few decades ago, beating their kids less, stealing fewer car stereos. There might indeed be moral decay, but that doesn't answer why fake license plates and not some other thing.

I suspect the reason for greater fake license plate use is the same reason for most products picking up: people are selling them, people are hearing about them, etc.

I suspect speeding has many causes, among them the fact that cars these days can accelerate easier and ride more gently at high speeds. People mostly drive however feels comfortable.