My experience
1) was growing up in my teens, we had a khyber took the khyber with the driver got rear quaters and rear windscreen het black tinted and a silver antenna for looks. That was new hear night too much extra police.
Had a hard scold by my father. After a few days got it removed.
Got my 2002 vitz rear windows and rear windscreen tinted lightly just for looks looked decent. But with time they got blur removed them and thot removed gave a wholelot clear vision which was excellent.
Then got only quater glasses tinted to match black shades. But ever since I'm into practical driving shades/tints are a hurdle in my driving. Although there are times when the sun is exactly on the driver side window and I feel like having a shade.
But sun glasses do the job perfectly.
So I guess tints are for looks only.
My recent visit to china 99% cars are lightly tinted all screens and all windows probably to keep the car cool. That too in 3M tint paper.
My 2007 vitz has rear windows tinted. I have been stopped 3-4 times and asked to lower windows and then let go. So iguess tinting is a stupid idea and its a hassle to deal with these *******'s. So keeping clear is the best idea unless ur involved in something illegal