Mortgage protection insurance isn't PPI any more than life insurance is, IMO, it's term assurance for the duration of your mortgage. It protects your mortgage against your dying or certain other circumstances - I would never take out a mortgage without some insurances.
Credit cards and loans, on the other hand, the PPI protects your repayments and many of us were conned into buying it - my employment T&Cs means I get 6 months' full sick pay so unless I were off ill for a very long time, I'd never need to claim- they refunded me.