Nifty Knitting: paintings by played sims can't be bought on plopsy?

I can't buy my other Sims creations on plopsy when I change household. I think it's by design, but I could be wrong. So I create retail lots to sell my paintings and knitted crafts, plus other things like carvings, candles, flower arrangements, preserves and more. So that way, when I've played a Sim that's crafted a lot of unique items my other Sims can buy them instead of having to be creative themselves.