LOL at so many justifying their tint because of heat rejection and a strong summer sun in their region.
But ultimately, if one thinks that it simply
looks cool to tint the windows and/or windshield dark based primarily on aesthetics, that's fine too.
Looking cool is oftentimes more important than
being cool inside the cabin.
We car enthusiasts spend
a lot of money on items for our cars simply because they "look cool", with no measurable or meaningful benefit other than aesthetics. So if you live in a country where it's chilly and dreary much of the time and where summers are short, and you
still want to put a 5% limo tint on your G8X, have at it.
We own M cars, most of which never set foot on a track...so, many of us are posers anyway, and have no real need for 500-hp cruise missiles on the street. And then we mod the hec out of them, oftentimes for additional performance,
for the street.
So you do you, because
you paid a lot of money for your car, so mod it as
you wish, for whatever reasons you decide.
No justification needed besides "it's what I wanted".