There's been some really good DLC, the main Dishonored DLC was fantastic and I generally like how Payday 2 has handled it too.
Tims change. It made more sense to package everything up as a single product when you're only dealing with retail.
Of course some companies get it right and some get it wrong.
How many games have only a single unit of DLC? Ideally and in the past, publishers would have bundled all of the content into an expansion pack. There is an important distinction between an expansion and DLC. It has nothing to do with the delivery method. It has to do with the quantity of content and how varied it is in one package.
Tims change. It made more sense to package everything up as a single product when you're only dealing with retail.
Of course some companies get it right and some get it wrong.