Whenever I see a topic like this, I always wonder if EA sees the player demand for it. My impression of EA is that they are a very traditional, numbers-focused company. If they don't see the numbers, they will not put their resources to develop it.
One quick look at the Gallery and Elders very rarely come up. Toddlers are less rare but still much fewer than the households that are Young Adult/Adult-only. I don't have all the data--the Gallery is PC/Mac-only and not everyone uploads to the Gallery--but if I were to guess why the focus on YA/A, it's probably simply because it gets the most numbers. Of course, the catch-22 is Toddlers and Elders get fewer gameplay features than YA/As, which also explains the lack of numbers. So... it's a complicated cycle, to say the least.
To be fair, I am also guilty of focusing too much on YA/A. That's why I've been consciously trying to add more Elders and Toddlers, even Elder-only households. I should also probably upload them to the Gallery... if and when I finish my world rebuilding project :sweat_smile:
