history: i get frustrated when i let someone out in traffic and dont get a wave i hate when i let someone out in traffic and dont get a wave That has always bothered me as well.  I mean_comma_ how much effort does it take to just wave as a thank you?
current: thats what i am saying! common courtesy
next: People do not seem to have much of it these days unfortunately.  I promise if you ever let me out, I'll wave.