If it's not a big deal, then why so many comments trivializing people's reasons for not waving?
If someone chooses not to wave because they are focused on their driving, it doesn't mean they have no confidence in their driving skills - it means they choose to keep their attention on the road and not on that little person in a great big box going the opposite direction.
If you like to wave, keep waving. At some point, you'll cross paths with another waver and you'll get satisfaction. If you're not a waver, just go on with your day.