Here in the USA it seems that depending on what city you are in influences what car accessories are actually popular to you and your friends. And a lot of it actually has to do with the weather.
Case and point, in the Ohio Valley and the northeastern states like Pennsylvania, New York or New Jersey, one of the most popular truck accessories on the market would be the truck tonneau cover. This is truck accessory purchase is totally weather related because people in the northeast have to put up with a lot of cold, wet and snowy weather in the winter and want to try to keep their truck beds dry if they can, and keep the snow out as well. Yes, a tonneau cover looks nice, and yes it might help you save a few gallons of gas on a nice long trip, but the main reason that customers ask for the tonneau cover would be to keep out the weather.