What happened to The Sims?

I'm just gonna throw in my bit of feedback. I also love TS4, and I appreciate what the Sims team have done for us. However, I sometimes do wonder how some of these extremely game impacting bugs slip through with the release of a new Sims expansion or pack. For example, Seasons introduced the non-interactive sims bug where sims would barely if at all interact with each other. When Island Living was released, it came with disappearing sims when inviting sims from different worlds to come to Sulani with you. These are pretty big and serious bugs that will ruin a game. Currently, the singing serenade is completely broken. Your sim will start singing and then freeze with his or her mouth only moving, lol. I personally would rather have them spending more time on fixing bugs before releasing new content, but that's just my opinion. I like new content, but I also like not having serious bugs.