I hated this aspect as well but I found a nifty trick that still works.
What you do is go into house/apartment via build with just yourself no sims.
Once you are there, it should show all the furniture that used to be there before it was empty.
If not, this may or may not work, but if so do this next step.
Place a chair down. Any chair, I usually use dinning room ones. You just need one just place it anywhere.
Then just go out of the build and back to the map, try moving your sims into that apartment/house again and it should give you the furnished option again. And when you go in with the family, it should have all the original furniture back.
Hope this weird trick works for you, as it does for me!