We already have a good romance system and plenty of romance items throughout most, if not all the packs. WHY do we need a romance pack or free babies, for that matter? We already have toddlers.
You might as well say why have any pack. Why have werewolves when there are already other occults? Why did we need Seasons when we already had sunshine and some plants? Why did we need Realm of Magic when we already had the voodoo doll? People want it expanded on, clearly. Romance is a big thing that can play into a lot of people's storylines, and the system isn't really that sophisticated. If you flirt with any other Sim, as long as they aren't Unflirty, you can start a relationship with them. A system for attraction/repulsion that's a bit more nuanced, and activities you can do as a couple other than woohoo, would be very welcome.