A lot of early games (which were incredibly simple) had game-stopping bugs. These are the infamous Kill-Screens which were only experienced by really skilled players, but it's the same underlying principle. The player doing something the programmer didn't expect, namely not getting killed off fairly quickly.
My first real experience with a game-stopping bug happened with the classic Atari 2600 game, Pitfall. For whatever reason, if I attempted to play the game on my system (and I tried three or four different copies), I could only play for about five minutes before jump glitches started happening. When I pressed the jump button anywhere on the screen, I'd be swinging on a vine... whether one existed or not. A few minutes later, it would get so bad that I couldn't jump off of a vine without immediately attaching back to it. Same games worked fine on every other system I tried it on, so it was an isolated hardware glitch. Great game, everyone loved it, but a buggy waste of money on my end.
Games today are really complicated with all sorts of interactions going on. Flaws in hardware or software are in the mix (we're talking imperfections that are unique to your console). The various AI routines are interacting with each other in unpredictable ways. A lot of these glitches are one-offs, something you're likely to never see happen again. Others can be replicated. Some are known glitches, others unknown... and it can take months of millions of people going out and playing in all sorts of ways to find the unknown ones. The more complex the system, the more mistakes are going to creep in and fixing one often creates another one somewhere else (think about how your body acts... you take one medicine to fix one problem then have to deal with another problem elsewhere, hopefully smaller than the original one).
This doesn't excuse a company from releasing a game with show-stopping bugs that are heavily reported within hours of release. Those are obviously known issues that they approached with the "we'll patch it later" mentality. But especially with open world games, you're going to find glitches and bugs. The worlds are simply too big for a small handful of play-testers to find all the potential problems. As long as the game is easily playable and can be finished under the most common circumstances, then I think they did their job. And when the bugs come out that along the lines of "when the car is struck from behind while the air condition is on and the right blinker is on, then the car explodes", you fix them if they're deemed serious enough.
