Like finding empty spaces in a tray of chocolates, but worse

In a perfect world there would be no such thing as a switch blank. You’d have enough money to buy the car with every conceivable feature fitted. Or, if you wanted a simpler, lighter car, that version would have a console and switch panel designed for that exact level of trim. If there were four switches required for the four functions, there would not be a fifth and sixth hole stoppered with an unmarked plastic plug.
Ideally, the designers would arrange the buttons so that there was no evidence of anything being omitted. For the manufacturer this might mean designing and tooling a large number of variant parts. But in a perfect world, you wouldn’t mind paying that little bit extra. What we find in reality is that manufacturers need to make hard-headed decisions. On the one hand they want the possibility of fitting as large a number of functions as possible but also they want to have, on the other hand, the possibility of selling the car for the lowest price possible.
A circle must be squared. The resultant squircle is the existence of glaringly obvious non-functioning buttons and blanked-off switch holes around the dashboard. They say to the owner: you were too cheap to opt for the rear-view mirror demisting function. You did not have the wherewithal to afford the heated rear armrest or the electrically-actuated glove-box closing feature.
1997 Volvo 850 centre console
The other puzzle is the existence of switch blanks on quite expensive motor cars. My research indicates that the highest ranging prestige brands from continental Europe are among the worst offenders. There are Porsche Panamera’s with switch blanks. Conceivably even Porsche can’t fit everything as standard despite their high prices but their customers are not so price insensitive to be able to pay for custom trim, designed for the number of buttons for that trim level and no more and no less.
Looking backwards, it was drawn to my attention that the rear doors of the Peugeot 604 had grommets where the manual window winders were to have been placed despite electric windows being standard on the car in W. Europe. You’d think the entirety of W. Europe was large enough a market to warrant a grommet-less door card.
Anyone who has ever peered inside a Mercedes W124 will find a wealth of switch blanks, none of which quite fit the panel they sit on. Is this phenomenon still with us? It has been a while since I looked at an E-class interior. I must suppose that as more and more functionS migrate to touch-screen interfaces, the days of the switch blank are numbered.

Deleted option: remote control for rear ashtray?