The diplomatic answer? For creativity in builds, to make certain types of environments, and to have space-saving items for the family.
The honest answer? Because people hyperfocus on individual objects that were in previous Sims games until they obsess about it and expect it in every single content release thereafter.
If you doubt me, look at Murphy beds. People were flipping out that they weren't in Discover University. I mean... Really? How many people actually needed those?
I don't get the object fixation either.
