I have the same opinion as you that animals should not have their lives taken away from them just for them to be skinned for their fur. I also believe that most animals should be under the Protection Act 2000. I say most because like you said, leather is very much the same as fur, it is made out of a animals skin and leather is something everyone wears. Though most leather usually comes from cows and alike which are also farmed for their meat so they are not exactly killing them for their skin, its more of a bonus.
However I think it would be difficult for people to use the fur of a naturally deceased animal because by the time anyone finds their carcass, it would have been partially or completely decomposed and therefore, the fur is unusable for crafts.
One of the reasons why wearing fur is illegal and immoral is because the process of killing the animal without damaging its fur. This involves the trappers strangling, beating or stomping them to death, while animals in fur farms may be gassed, poisoned, electrocuted or have their necks snapped. The major issues with these gruesome methods is that it is not completely effective and some animals regain consciousness 'while' being skinned. Another problem with fur hunting is that alot of the extinct and endangered species are in that situation because of fur hunting and poaching, such as tigers and elephants.
More information on fur can be found on the links provided below: