Downloadable content has been a controversial topic since it first popped up in the gaming world. Starting out almost immediately on the wrong foot by using the service to sell players things they didn't want or need, like the infamous horse armour for Oblivion (oh how far the industry has fallen since that was the most pressing issue), adding extra content to a release is as touchy of a subject as it's ever been.
The caution surrounding DLC is for good reason though, as while there have been some amazing instances of post-release content outmatching the original product, there are some developers that have relied on extra DLC far too much, to the point where the actual game they ship out to players is far from the complete package.
Featuring plot points that go nowhere or endings that suddenly cut to black without any resolution, buying additional DLC can be the only way to make sense of the stories of these games.
Some studios are worse than others for releasing an incomplete experience with the idea that the gaps can be filled in with additional expansions later though, resulting in a plethora of popular titles that the majority of players never got the full picture of.