These days in games industry there are a lot of downloadable content (DLCs) and there are always or often not for free. of course these DLCs are different from game to another, sometimes its an addition to the story so you would understand it more and sometimes its additional maps or modes in Multiplayer or even new weapons. There are some pros and cons in DLCs in my opinion I will talk about them from a player view ,so lets get to them .
There are some pros in DLCs specially when the game developer gets new ideas about the game while its already came out so he can add them as a DLCs, he can gain profit from it and entertain the player. Also in mMultiplayer if you get bored from the maps you have and the modes then you can buy a DLC for new maps,modes,new weapons or new features that make you more interested in the game like what Call of Duty for example does.
And like I said the DLCs are different from one game to another, some may give you new cloths or characters like in Assassin's creed black flag or some will give an addition to the story from another angle like in The Last of US.
Everything has some pros and cons and when it comes to DLCs one of the main cons is that some DLCs are really add something to the game and worth the money while some DLCs are not. Also some games developers may remove some chapters or make the game end in some point so you need to buy the DLC for the missing chapters or to understand the game more, while it should be in the original game already and you shouldn't make the player pay again for it. And don't let me start talking about multiplayer thats another story, like when a developer save some ideas,maps or even weapons that make them in the game are so few then you need to buy DLCs again to have them.
In summary I'm not against DLCs but the games developers need to make them worth the money and not just remove things from the original game but to add things to it because we already paying $60 for it. And specially now because almost every game has to come with DLCs.
look at the pictures below it describes the way before and now and hopefully not tomorrow :)