In the So Cal of my teenage crusin' days in my muscle bound '74 Nova Custom, there were many restrictions placed upon car owners for type and placement of window tint. We'd go to extreme lengths to not get "popped" for having our car windows tinted darker than legally allowed.
Functionally, window tinting keeps the car cooler in the baking summer sun.
Aesthetically, it looks cool. Least, we thought so. Teenagers...hrumph.
I recall times where my passenger and I would frantically perform the "roll down the windows (no power windows for me) ritual" whenever we were in spotting distance of a black and white.
I even knew of a guy who swapped license plates on his gold, illegally tinted '81 Trans Am with that of his Aunt's gold and legally tinted '81 Firebird. He took her car down to the CHP office as proof of the correction, and got his "fix-it" ticket dismissed.
Here in Oklahoma, it seems that any tint of any kind, placed just about anywhere (except on the front windshield) is legal. Everyone around my town seems to have Presidential limo tint on their pick ups, SUVs, Towne Cars, and 300's. Makes sense here, especially in the baking summer months (that seem to last from May to October).
A street wary product of East LA, I'm not in the habit of staring anybody in the face more than necessary. You learn not to make direct eye contact that may get you a one way ticket to an uncomfortable and/or dangerous confrontation with who know's who (or what). An extension of that is not looking into cars -- especially those with dark tinted windows.
So as a habit, I don't fixate my stare on whomever is sitting behind the wheel of any vehicle. Combine this with the fact that people here must forget that their car windows are protected with the equivalent of SPF 1,000,000, and the results are that on several occasions now, I've been nicely chastised for not "waving" at people in cars that I happen to walk right by.
Sorry people, can't see you behind all that smoked and dark glass. If I don't wave, it's not because I don't like you or don't want to .
I just can't (dark tint) and won't (avoid confrontation) see you.