Thank you while driving?

When i was a child i always saw my parents wave 'thank you' or 'excuse me' as they switched lanes. Naturally, that was something i learned to look for in other drivers. Years passed and i learned to drive and i leaned to switch lanes, always with a 'thank you' or an 'excuse me'. Now as a driver i continued looking for the wave' from drivers. It was never common persay but it did happen rather often. But now, not even my parents use it. I dont think ive seen anyone wave while driving in a year maybe. What happened?