There are a ton of plot hooks if you bother to look. Yes, it may be up to the player to actually do anything with them (and a lot of the families don't have the right relationship levels indicated by their writeups, but that's not a ratings issue) but they are there.
There's also a bit of lore in the descriptions of several items in the Buy catalog. Maybe not as much as previous games, but it is there.
I mean, I personally think they could get a bit darker without violating their rating code, but I understand why they don't. And honestly it's easier to take the game darker than intended than take a dark game and lighten it up without going to parody levels of melodrama.
