The courtesy wave

Whatever happened to the courtesy wave? I was driving through a lot of construction this weekend, and I'm a pretty charitable driver. I'll let cars merge in front of me. But out of the nearly ten cars that I let merge, only one gave me a courtesy wave. And it was of course the big ass truck, not any of the sedans I let through.

For those of you that have no idea what I'm talking about, SHAME ON YOU! Whenever anyone lets you merge into a spot that he needs to slow down for, etc then once you're in, you should wave to the guy that let you in (usually with your right hand through the rear windshield).

Please practice the courtesy wave as often as humanly possible.