I hate how many cars I see these days with windows so tinted that eye contact and waves are impossible.

It feels dangerous to be unable to see the driver through their side window (eg. 4-way stop eye contact on who goes)

Agreed! It's a small but satisfying interaction to have that coordination and unspoken communication with other drivers at a 4-way stop.

I've taught my kids when crossing the street to make eye contact with drivers to make sure they see you. Drivers with smartphones unfortunately add to the challenge.