If everything is on the car already for economy of production, why don't they just include it in the main price rather than charge extra for it?
It's a fair point and to some degree we see far more standardisation to wider degree of options in the base modesl eg air conditioning is almost standard in most base models these days. Where even in up market brands like Mercedes it was an optional extra upto about 20 years ago. I remember my first Mercedes in 1993 I paid to have the option of speakers, aerial and stereo put in the car, when it was pretty much standard in other brands such as Ford , Vauxhall............go figure, some marketing guy thought the customer having the right to choose what stereo equipment they wanted in their Mercedes was an expensive option they could afford and therefore put no equipment in as standard. Same as heaters used to be an optional choice in many UK cars, staggers belief today.
Problem is that the higher the standard spec the greater the base model price becomes making them increasingly less affordable, removing the option of low cost motoring for many.