Just as the title says, is there a reason we can't do so and get some of the materials back as well as deal with any excess furnshings thus freeing space from bank and boxes?
Well, for the same reason for which we cannot sell the furniture we buy from vendors for the same amount of money, or at least (at least!!!!) half the sum. So you have to farm for more gold and resources, fill in your bank with junk in order to buy eso+, stay in the game longer, even if it brings no value to you... Simple business, meh.