True; I have had several poor-quality hardcover whose binding has come loose and the entire cover came out. Oddly enough, I've had a few paperbacks who stood up to much use. So it does come down to the quality of the individual book
Typically, though (and I've owned several leather-bound books, not just Bibles but other literature as well), where the extra money for leather is going to pay off is in the corners. After much use, especially upright shelf storage, a hardcover will have rubbed-off corners, whereas the leather should remain intact. Leather-bound books also are much softer if you hold them open in your lap for long periods of time, though not as soft as a paperback.