These days, you'd be hard pressed to find a car or truck without cup holders in it. A part that is both superfluous and mandatory, it's just a small plastic hole for either the driver or the passenger to place their non-alcoholic beverage of choice while they travel to their destination. It may not seem like such an important part, but it's basically a mandatory component in the design of today's vehicle interiors. The arguably recommended eight glasses of water a day can be partially contributed to by bringing along a water bottle and having somewhere to put it while you're not sipping from it. It also comes in handy if you're feeling hungry and pull into a drive-through restaurant. Basically all combos come with a drink and the cup holder is meant for precisely this situation.
Modern car and truck interior focus a lot on the aesthetic appeal and since the cup holder is a mandatory element, it's a part of the initial design process from the very beginning. Most of them are situation in the center console in a configuration that works with all the other components in that area such as the shift lever, parking brake lever, and any other buttons related to the transmission. There are vehicle designs that placed the cup holders a bit higher up in the dash near the air vents. It could be that these locations are easier to reach, but it's likely just to stand out from the crowd. Still other designs have placed some in the doors near your feet. You'd see this design in small SUVs where having an extra water bottle on hand is nice.
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