I have a dream. That when a big shooter is released, at least some of its downloadable content caters to the crowd that prefers to game alone.
Think about it. Despite being games that are defined in many ways by their singleplayer campaigns and heroes (Master Chief! Captain Price!), series like Halo and Call of Duty are prolonged not by more singleplayer content, but by multiplayer map packs. Boring.
Can't one series, one day, stump up the time and cash to do a little singleplayer DLC instead?
It'll never happen, of course (well, it usually never happens). There are two reasons big shooters get maps packs (or zombie packs) as downloadable content: they're catering to the large multiplayer fanbase shooters develop, and they're relatively cheap and easy to make.