Video Games and Storytelling go hand in hand nowadays. Even the most violent of shooting games normally have a big cinematic story to tell. Red Dead Redemption, Grand Theft Auto, Halo, and Call of Duty have received a lot of praise for their stories and storytelling, even when being criticized in other areas. But why do we find Storytelling so important nowadays? Why does it seem standard that every video game, especially shooter games, need to have some kind of story?
We Need a Reason to Get Invested
I think the first reason is it gives us a reason to fight, a reason to play the game. Say you bought the new Call of Duty, and with no explanation it dropped you into a level with no dialog, no named characters, no objectives, no defining marks on anything, and enemies that didn't make a sound. Would you have fun? Would you feel like you were accomplishing anything? No, you wouldn't. You might have fun for a bit, but ultimately you would feel like you were wasting your time.
When your playing a Call of Duty game, you feel like your saving the world. In MW3 you end World War III, kill the greatest terrorist in the world, and save the world from nuclear destruction. That's a whole lot of accomplishment. In Halo you save the human race, and to a greater extent every being in the galaxy, from total destruction 4 times! 4! That makes you feel crazy accomplished by the time the credits role, like a true hero. In Red Dead Redemption, you're trying to redeem your criminal past with good deeds and morals, and even when you are gunned down by the corrupt law in the end, you get the sense that you succeeded.
You need a reason to fight. We don't live in the Wolfenstein or DooM era anymore (even if they did have minimal stories). You can't just be dropped into a middle of a battlefield, kill a bunch of enemies, then be expected to do it another 20 times. You need reason.
Players Get Connected to Characters
You ever play the Halo games? Did you play all of them? Did you beat Halo 4? Did you cry when Cortana died? Rhetorical question, we all cried. You know why you cried? Because you were connected to her character. You knew her, you liked her, and throughout four games in the series she was your companion who helped you through the game. So to see her die, probably upset you. And this is where the second point comes in, players enjoy the game more when they get connected to the characters.
You play Pac-Man? Do you give a single shit if that guy gets all the pellets or if he gets killed by Ghost's? No you don't, cause you don't know anything about Pac-Man. He's just 25 cents to you (if you live in America, in the 80's). What about the Doomguy in DooM. If he had a heart attack mid-level and you suddenly started playing as Doomguy 2, would you care? Probably not.
But what about when Soap Mactavish died in Modern Warfare 3? Maybe you didn't flip like Price, but you were probably at least upset knowing you would never see him again. Did you struggle to choose between saving Roman or Kate like I did? I had to balance the pros and cons of both, and truly think about who I liked better before making my decision (I went Roman). Don't tell me the thought "Well, who do I like better" didn't at least cross your mind.
We like it when we can tell stories about characters, decide who we like and who we don't, when we can know who they are.
We Like the Cinematic Quality
Games nowadays are kind of like Movies. They have cutscenes, dialog, scripted sequences, characters, story specific missions, etc. This all builds up to impressive and fun stories to tell. Even if you aren't one who likes having to replay a scripted sequence or wait til a level loads so you can skip the cutscene, you probably appreciated the story the first time through thanks to those things.
We Love Speculating
Speculation is one of a couple things that keep internet gaming forums alive (along with Game Hate, Game Dislike, Company Hate, Uncalled for Hate, and Praise). Speculation is a great thing for fans of a series, both creatively and as a source of fun. Speculation is what fueled the Halo series for a long time. Bungie gave us the pieces of the Puzzle in Halo 1, and they built the puzzle up in 2, 3, ODST, and Reach while never fully revealing the puzzle. That was left up to the fans.
The Zombies Gamemode in Call of Duty is notorious for Speculation, in fact some parts of the storyline are BASED on fan speculation that Treyarch liked and chose to use. Whole communities of gamers come together and try to figure out what every little bit of every zombie map could mean. See that bloodstain next to the single shard of broken glass? It just revealed the whole zombie storyline from now until Black Ops 17.4.
At the End of the Day, Stories Are Just Fun to Follow
Stories are fun, that's the bottom line. It's more fun to play through a game that has a story, then to play through one with nothing.