Why would they do that, until they're confident they can release the game without major bugs? People have these weird ideas that development studios aren't super busy. Intellectually, they know. But they don't actually get it. The amount of effort required to release a professional version of even a small piece of software -- let alone a AAA game -- is a lot more than most folks realize. Bioware employs around 800 employees. That's around 800 people whose goal, at the end of the day, is successful releases of their games. That amount of employees alone should tell you the effort behind releasing games like ME:A.
So, in short, Bioware is doing their due diligence. Be patient. Quit getting OFFENDED or acting ANNOYED that there isn't an official release date.
They kind of did give us an official time of release when they said 'Holiday 2016.' Is it an official date? No, but it did give us a window of dates that we should expect a release on. That being said, games these days are released with major bugs anyway, especially EA games and the less said about the humongous amount of bugs present in DA2 and DAI at the time of release, the better. A game development company could be the busiest people in the galaxy, with a thousand employees working 24/7, all of them working on a single game for, say, five years and it will still be released with major bugs. It's unavoidable.
Doing ones due diligence is admirable, but when you give people a time of release (however vague) can you really expect people not to get mad when you give them another time of release, especially when this new one is just as vague?
Bioware has been working on this since 2012, probably longer since they could have made the announcement after they began work. They have (as I understand) around 200 people working on it, too, which as I also understand is around a full quarter of the company's manpower. This a ton of effort for creating a game, even by today's standards.
I don't presume to know anything about game development but when a game is being worked on for that long with that many people, you have to ask yourself what they're doing with it that they require more time.