They don't let you sell bootleg DVDs on a street corner because there is no code for that.
Skyrim needed DLC filled with code to let you build a house and in a very limited way adopt kids. You couldn't teach those kids to play soccer or fish, there was no code for that.
You must realize that it's NOT the "addition of code" which will make for more flexibility and liberties but exactly the opposite of it!
Another example:
There does not need to be "code" say which enables me to sell certain, items, in your example DVDs...or...whatever, say, items which would be rare to collect but nevertheless could play an integral role in the game.
EXAMPLE: rocks or bricks....which someone needs to collect....to build houses.
All there needs to be is a general code which enables trading, eg. exchanging of goods for money.
ONE person might spend his life in the game collecting bricks so he decides to become a builder which offers to build other people's virtual houses. (For a nice some of money in exchange of course).
The beauty of this is that there is no "specialized" code required (minus essentials that can apply to objects, such as that you can take them, own them, exchange them etc.)...and there are not even pre-set rules required, not even prices for items.
If an item, say, a brick to build homes is rare, someone can just spend time collecting them. He/She can set their own price if someone else wants one, he/she can set their price when they build a house for someone. (Or he can just build a house for someone in exchange for a car, stuff like that : )
The key here is that less limits and less code means MORE flexibility in what you can do!!