I can understand that raw leather is ugly, but I just made a boomrat leather couch and it's still at most only 7 (for excellent). I think cloth couches look nicer than leather in reality, but leather still doesn't have to be so bad. The boomrat couch looks pretty nice in red :)
Is this just to balance to resource investment of growing cotton instead of hunting?
What quality is the couch? If it's shoddy or awful that would explain why it's not pretty.
Now that I think about it, this is a mod issue. The couch is from the More Furniture Mod and. I just played around with Dev mode and all pieces of the same quality have the same beauty. I could have sworn I saw a normal cloth couch before and it was prettier. And then I thought it has something to with raw leather being -30. Silly me :/
Well, guess the mod needs some balance then