User blog comment:Lost Labyrinth/The Sims 4 - Gamescom Reveal/@comment-3982116-20130824192201/@comment-2201555-20130825222736

With regards to the beta tester thing, developers often pick a random selection of people who've expressed interest in the game to play a beta build of the game mostly for quality assurance. Their role is to report bugs back to Maxis and they'll update the beta build with any changes they make and go the "try it now approach" with regards to bug hunting. They did this with SimCity.

However, it's very possible that not /every/ bug can be found through beta testing, especially in a game like The Sims that's has some very complex coding and has to be carefully managed. Some bugs may never be fixed, they prioritise the serious ones above something like Sims walking across the street instead of upstairs (yes I'm looking at you TS3).

Of course, Maxis aren't the only guilty developer here. The nature of game development is that there may often be some bugs that are only found upon release, which explains the growing prominence of "day one patches" for games. While some bugs are forgivable based on the game's nature, some are ridiculous yet they're never fixed, usually on the basis of the bug not being a big deal, the developers (Maxis, Bethesda are just a couple...) being terrible at coding amongst other reasons. It's basically natural to expect bugs in most new releases, whether it's strange animations, bad netcode or horrendous lag. I'd agree EA do shine amongst the worst offenders when it comes to beta testing but they're not alone - it's basically what games development has become.