Being a father myself, I understand why the game decided not to include needs. You really have no way of communicating with an infant. Infants can't say "I'm hungry" or "I'm bored." They just have one universal way of communicating (crying). But then again, there were times when my little one wouldn't cry but there would still be something wrong with him (for example, he sometimes would have a fever, and I would have to give him something to make sure that the fever doesn't spike).
The point I'm getting to is that this is much more realistic. It's a challenge, but that's the challenge that parents face. You can always click the crib and click "Age Up" anyway. Real babies are much less boring than Sims 4 babies :D