If the windows were tinted so much that the cops couldn’t see the seatbelts, that is a violation. Why do some people need to darken their windows that much?
Because they want to? What business is it of yours what is in their back seat?
Exactly. Chicago isn’t in the sunbelt. Illinois allows tint of rear windows but not the windshield, and a lighter tint is allowed on drivers/passenger sides front windows. His tinted front-side windows looked to be pushing the envelope. Most criminals gangsters in Chicago with tinted windows do so to conceal their activities.
They do it for the same reason they wear hoodies.