Every part identical. Every piece the same. Manufacturers go to incredible lengths, to make sure that there are no differences. If a part is off by a couple of thousandths of an inch, it goes out into the trash. Computer chips are thrown away if they have mistakes that can only be seen under a microscope.
Marketing works the same way.
Somebody figured out that they could make a lot of money, if everybody in the whole country ate exactly the same kind of french fries. Somebody else figured out that they could make a whole lot of money, if they could get ten million people to wear the same kind of sneakers. The networks would like us all to enjoy the same kind of entertainment. The politicians would certainly like us all to vote in the same way. It would make things easier, for some people, if we all fit into a kind of cookie-cutter sameness, if we became identical consumption units, or earning units, or even salvation units.