The sunroof does add cost and weight, and the weight is […]
The sunroof does add cost and weight, and the weight is too high, which increases the center of gravity, which to some extent impairs handling performance. They also provide another potential leak path that could lead to premature corrosion. Of course, they also allow more light and heat (or cold in winter). But here are some things that are not mentioned in other people's answers, and you will only realize if you were an automotive engineer and followed the car along the production line.
The perforated sunroof roof lining is more flexible-making it harder to install during assembly. In our production line, we have a cycle time of 83 seconds, so people only have 83 seconds to install the canopy before the car can reach the next station. Our sunroof roof lining tends to fold in the middle (where the holes are weakened), so we must immediately “contain” this problem by adding reinforcement rods on the B side (below) of the roof lining, and then expensive The replacement of the tool adds the reinforced channel formed, so the reinforced rod can be removed (because the unit price of the rod hurts our profit margin). Naturally, we had to use stiffeners for a while and "build ahead" to build enough canopy to cover production, while the canopy tool was changed to add molding channels. Nothing is easy.
Sunroofs require motors, wires and electronics / controls. However, this is not surprising. Surprisingly, electronics and motors need to pass EMC tests, which is both time consuming and expensive. Some safety features must usually be added to prevent people from pinching their fingers when the sunroof is closed. Now let's talk. Your average "Joe" or "Jane" customer may not recognize the Webasto sunroof switch, let alone realize that the color of the plastic or lighting used by the switch buttons may not match the rest of the vehicle (as they are designed to make hundreds 10,000 switches and sold them to multiple customers with different internal colors).
Finally, let's talk about wind noise, NVH (noise, vibration, and harshness) and BSR (hum, squeak, and rattle). The sunroof and its added parts are the minefields to solve such problems, from the wind shaking of fancy pop-up windshields, the internal parts to the potential rattling of the sunroof "itch", when the internal shutters are under closed or similar friction When sliding open, the internal shutters rub against the canopy fabric.