Because you can see exactly what you are buying. The IR and IR+ ranges give you a spread of shades from near-invisible to very dark, each with its own published specifications, so the look and the performance are separate decisions you make deliberately. The nano-ceramic construction keeps the glass clear, and the film is fitted by an installer who has inspected your Tesla's glazing first.
Between the shade range and the specifications behind it, there is a sensible option for most Tesla owners, whether you want the car to look untouched or noticeably darker.