Once upon a time, a release date was the date the FINISHED PRODUCT was released -- not the beta.
It doesn't help that modern games are enormously more complex than games from even 5-6 years ago. You think past games for PC and consoles in the 90s shipped bug free? Hell no, and you're just ignoring the facts if you claim they were. DOS games, NES, SNES, Sega, games for ALL of those platforms were no stranger to bugs, some more than others. Looking back and claiming that past games shipped "finished" with no bugs is not only ignoring the truth, it doesn't even take into account the MASSIVE scale by which games are made these days as compared to their predecessors.
How long do you think it took to debug a large problem on NES Mario Bros for a team of developers? A day or two maybe, if that? Try that with millions of lines of code in a game environment where SO MUCH is interconnected and context sensitive. And many of these issues CANT be discovered with a few people QA testing, there are just too damn many avenues to take in a game like this for them to test every possible scenario in every possible order to check how A affects B when also considering the impact of C through Z and so on. The QA testers were always moving on to a new build, day after day after day, testing a new build to fix something or add something from the previous build, when unknowingly somewhere between build 500 and 501 something was overlooked and made it into the final master because there was not enough time to go back and thoroughly retest everything tested prior. When it was released to a massive audience, some issues were quickly discovered simply because of the sheer number of players hammering away at the game in their own particular way. Once those issues were discovered and Bethesda could see the symptoms, that points them in the right direction to patch but it is still a very delicate matter.
They are on their way to treat Skyrim to three patches in less than a month from launch. That update schedule is much more aggressive than how past TES titles were updated (granted 1.2 was a little TOO aggressive but they've settled on a good pace), and still the whining bellows forth, that it isn't fast enough and we need the game perfect NOW WAHHHHHHH!!!
ffs...