My late quaker, Lucy, had a foot that got darker and heavily scaled because her leg had been broken when she was little. The foot wasn’t getting good circulation and she didn’t use it much in her last five years, so I think she didn’t wear away her foot skin
The leg rebroke about five years ago when she (possibly) jumped off her cage to come get me when I was sick. She couldn’t fly at all (injuries at same time as first leg break) and I found her with a broken leg on the floor. After a long difficult recovery, her foot had to be moisturized because the skin just wasn’t working right any more.
Foot problems are serious in parrot and birds in general because they can lead to systemic infections.