exactly...
exclusiveness/upmarket feel is the main reason.... you will find plenty of grey dashboards in one shade or the other everywhere... like majority of hatchbacks, sumo's, qualis'es or even in mini-trucks I guess... beige is primarily seen in luxury cars! if beige was commonly used everywhere, it would not be a surprise if people had an obsession for grey instead
no offence meant, its only about the color... quality is different issue, like paying extra premium for beige-leather is quite understood. but most of the first car buyers may not notice that while "leather" is really costly, "beige" should come pretty cheap and its the later which matters much more
many people refer to grey plastic as "cheap", IMHO "too-common" or "boring" could be better words to describe it.