Why is activision so greedy?

To be honest, I don't really mind Call of Duty. I play Nazi Zombies a lot, I usually finish veteran singleplayer (although cod5 was hard), and I have a bit of fun with multiplayer, until it gets old and too many people use cheap weapons. Anyway, I wanted to know what all the fuss was about with the new map packs, so I purchased Ascension. It was an alright zombie map, although the color made it a necessity for me to turn on the power before I got a headache. The multiplayer maps were completely terrible, with the exception of Stadium. They were all dull, had almost the exact same color scheme as the other maps, and were very bad, containing many camping spots. I didn't think too much about it. Honestly, I thought the map pack was alright. The price irritated me a bit. I payed around 10-15 dollars to buy a pack of terrible maps that should have been free. Then, activision released a new map pack, Call of the Dead was the name of the zombie map, which was all that I really care about in Call of Duty anyway. I wasn't so hasty to buy the map pack yet, so I waited for a while, expecting a sale to come out soon, sort of what Bungie did in Halo. No sales come out. I start watching the videos about the new zombie map. I couldn't even believe how terrible it looked. They try to add a new plot line to the map, which, in my opinion, was total crap, they seemingly took the ship portion of the Black Ops campaign mission, Project Nova, and added some terrible easter eggs and a devilishly hard sequence for one achievement. That is ridiculous! Don't you think that Activision should have done what Ubisoft did with AC:B and made map packs free? Seriously, that's about 90 dollars down the drain for one game with a few added map packs that should have been free, in my opinion. Maybe instead of working so hard on devising schemes to suck all the money out of Americans, they should have worked harder on the whole game, such as fixing campaign missions, adding checkpoints to the game so that you don't have to complete half the campaign mission with one checkpoint, fixing spawns in multiplayer, balancing killstreaks... anyway, that was just my little rant. So tell me, why do you think that Activision keeps trying to squeeze money out of us? In fact, on Steam (which i use) most games of equal value to black Ops are about half the price of black ops itself! Why do people keep buying map packs if they have to pay so much for it?