The last paragraph deserves the emphasis. Rebinding a book that has any collectable value usually destroys most of it, because an original binding in poor condition is worth more than a beautiful new one.
For those, a custom box or a slipcase protects it without touching the book. Considerably cheaper than a rebind as well.
Rebinding is for books you love and nobody else values, which is a large and worthwhile category, just not the same one as valuable books.