Why should anybody other than you and the people in your car have any right to know what you're doing in your car? It's a matter of privacy. Nobody has any reason to be looking in. Window tinting has a long and storied history of protecting the inhabitants of cars from the prying eyes of those outside.
If you've ever been impressed by the shielding power of a good tinted window, I'm sure you thought about getting them yourself. They're cheaper than you'd think. They can be installed in minutes.
If you're worried about the legal issues regrading how dark window tinting can be, ensure you check with your local laws before deciding on a job to get done.
Window tinting also provides valuable protection from the harmful rays of the sun. The sun's ionising radiation is a primary cause of skin cancers, including melanoma. Tinted windows block ultraviolet rays, which are the harshest type of ionising radiation.
This also means that your car is much easier to keep cool in summer, especially if your car lacks an air-conditioning system, or if you want to keep air conditioning costs down.
In any case, window tinting is a fast, easy, affordable, and painless process that gives you a place where absolutely no one but you can see what you're doing, which is something really everybody ought to have.