Don't be so quick to jump to conclusions.

• Including good cupholders isn't a trivial problem, at all. From silicone cushioning to automatic cup-locking, to lighting, to thermoplastic insets, to accommodating a vast range of different sizes, from coffee cups to super-gulp 1.5 liter monstrosities, the list goes on. Compare to: What is the optimal can size, and form? Seems easy enough, yet far from a "solved" or trivial problem.

• There are immense safety issues: If they impede the driver in his normal operation of the car, the manufacturer could be liable to lawsuits. Mustn't impede airbags, even using the largest fitting cups, or liable for lawsuits. Must be secure from spilling (not only an issue for 4x4 offroaders, but also for normal cars on the occasional bumpy road, or going up and down a ramp), or liable for lawsuits.

• There are people specifically responsible for designing cupholders, up to whole companies, in fact. I remember an article stating that there were man-years dedicated just to the cupholder for some specific car model.

• Real estate in a car is at a premium, especially the easily accessible portion. Accommodating someone who wants 3 beverages within easy reach (such as yourself) may annoy someone who just wants one, and doesn't like the way so many cupholders wreak havoc with other elements of the interior design (which you listed as an even bigger priority).

• Outside of the US (say Europe), cupholders have a much lower priority (at least according to an article I'm just now reading). Eating and drinking cupious amounts in a car - while not unusual - isn't as common everywhere as it is in the US. (Obviously this point doesn't apply to car models that are manufactured exclusively for the US market.)