Conspiracy theory! Previous CODS show DLC to be varied in quality and also subjectively good/bad to the individual!
Not to mention the proportion of people who buy DLC is pretty low - anything from 10 - 20 % of users at most. Not the best model for getting profit. They already made 4 gazillion dollars - they already got yer monies!
MW3 stock maps are teh worst ive ever seen.
same with BF3 stock maps.
lot more effort goes into DLC maps.