Two letters. E A.
EA thinks that all of its games are too hard.
EA thinks all games should have multiplayer.
Basically EA is catering to the low attention span of the Call of Duty people. Dragon Age is made for more mature people with higher attention span, people who are around 30, not 13. As a result it is outside EAs target market.
You have to remember EA loves microtransactions, and it has a reputation for aggressively targetting the young casual market. It is easier to convince a 15 year old with little finincial experince to part with their money then it is someone who is 35. At that age they have not yet learned the value of money or how to handle it. So if you are an unethical company only interested in money you want to make a crappy multiplayer game filled with bugs and sell it to a 15 year old. Then you fill it with microtransactions and patch it up later (possibly for a fee). Basically because a 35 year old has the life experience to know you are ripping them off, a 15 year old does not. Not to mention a 15 year old would probably be more willing to buy it because of the hype or it "being cool", which in a nutshell is EAs marketting strategy.
So why do they not make one?
Because its EA.
EA has questionable business practices.
EA targets the younger casual crowd, who are more liekly to tolerate such practices.
The older crowds would not tolerate such practices, and therefore EA does not care about them.
DAO was made for older crowds.