Sounds like a very silly attempt by the manufacturers to earn/safe some extra bucks.
I wonder if this actually works - while they might safe some money by not supplying some extra pieces (also because even if they would give it for free some customers just will not bother), disgruntling customers (like you) might easily cancel these profits out.

Reminds me of the case when I had to take US Airways for a flight back from the US. At that time I had to take an economy flight since it was for a training and I had to find out that the charged 5$ for the headset to watch the movies during the flight (first time that happened to me).
Made me wonder if they attract enough customers by making the price tag for the flight 5$ lower to make up for those who might not want to fly US Airways again (like me) because charging an extra 5$ for the movie on a long distance flight just gives a subjective impression of very bad service.