commented on Here's why The Sims 4 won't have pools or toddlers
The reason is actually very simple. Motion Capture. In order to get the animations to look more "realistic", you have to capture (or closely mimic) actual people. That said, doing so for a toddler is a VERY difficult task. Not just a motion capture issue (toddlers being known to have tiny attention spans), but hiring toddlers to model is a legal hassle. Pools are a more technical thing, for obvious reasons. It's not easy to emulate swimming to get it just right. The other thing mentioned that has a huge impart is personality and mood. Having different personalities for toddlers requires two things. Walks and crawls. This doesn't even take in to the account for the need to have toddler moods, which are legally difficult to invoke. My guess is that because of a deadline, they made a choice to work on other features that are more crucial for the base. We've already seen an expansion add "age based" content: Generations. That said, I think the whole concept of family building can take away from the doll house feel that existed in the first installment. A final word, pools are just... Tough...