I have seen horses like that. I watched one for a few years everytime I drove down a certain road. At first I thought the horse was neglected but realised it was just old. Whoever owned it must have carred deeply for it. It always had lots of hay, a rug when it was cold, lots of room to roam around and shelter from the elements. I noticed a month or so ago it was gone. Must have finally passed away. Not saying this horse is just old, I'm sure its a rescue case but some do get to looking like that in old age.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France