I understand and can sympathize with companies trying to get games out as soon as possible in order to meet deadlines and gain revenue, but now this trend has become commonplace without anyone really questioning why they're tacking on these added fees for content that is typically not worth the investment. If anything, publishers should just make the full game come out with all of the bells and whistles included.
To me, it seems as though DLC detracts from the overall experience, especially if other players want to discuss their experiences. It ostracizes those that either choose not to (or can not) purchase the DLC for the game their friends are playing. Often times, if the game has a multiplayer online feature, the DLC is required to play on certain maps (or stages) or it is required to equip special items for use. Those that do not have such content, cannot play with those that do. In some instances, it can be game breaking as certain add-ons disrupt game balance. Regular maintenance and patches can regulate this problem but it is still one that shouldn't exist in the first place.
In some instances, publishers have even put additional content (that could have been DLC) on the game disc itself, which the consumer can unlock buy spending additional money. Which means that the content is already on the disk. Therefore, my argument is that the practice of selling DLC is an exploitation of what should already be provided to the gamer. Essentially, publishers are using DLC as a way of increasing the price of games arbitrarily while being relatively inconspicuous about it.
When a consumer sells a game, the purchased DLC isn't included with it, and the new owner will have to purchase all of that content over again. From the publisher's perspective, that means they're finally making some money from a used game sale. From the player's point of view however, it means there's no way to recoup any amount of the money they may have spent on their DLC. This make a game substantially less valuable in the long term.
Now, that's not to say that all of the downloadable content is absolutely vital to a game. Some of the extras sold are secondary to the game itself or not deeply impactful to the main storyline on a large majority of games. However, overall, they are meant to enhance the game and further the development of certain subplots or elements to it. As such, it seems like a sucker punch to those that are driven by deep meaningful gameplay experiences and those that want to view games as a form of art (like a book). Imagine your favorite novel asking you to pay an additional $19.99 for enhanced backstories about certain characters or for more descriptive text about the scenery depicted in the chapter. It seems rather ridiculous as it shatters the immersion of the player. It just seems like a downright manipulative practice.