You don't NEED it. Some people don't get tint. But it will make the car cooler inside when it's sunny. It's also easier on the eyes. It's like a pair of sunglasses for the car.

It won't make the exterior paint last longer. Interior plastics won't fade and crack as much.

It's a must have for places like Texas and Hawaii. I'm not in a hot place, but I enjoy the privacy that it gives me (one-way tint).

I highly recommend tint or clear ceramic tint on all the glasses so that the interior plastics/leather stay supple overnight and not start fading, cracking, etc.  

Wax the car 1-2 times a year and you should be fine. 

Tint is a good thing here in TX. I recommend a professional do it. Nothing looks worse to me than a bubbled-up do it yourself tint job.

Make sure that you don't tint your windows darker than you state laws allow.