What if you could never work again?
Yes, you may have an income replacement policy in place, however, if you are never going back to work you could be in such a state where major modifications to your home are required. Or, having to deal with new expenses such as personal care.
As a complement policy to your income replacement plan, a lump sum payment from a total and permanent disability policy could be used for repaying your outstanding mortgage, and therefore with your continued income replacement plan your financial situation is improved.