Andrewa, I think you're confusing (compulsory) mortgage protection insurance — which clears your mortgage in the event of your death — and repayment protection, which guarantees to cover your monthly repayments for a certain period in the event of, say, you losing your job. The latter is optional but, as Brendan points out, institutions aren't always as open/candid about the matter as they should be...
Last time I remortgaged, I had to sign a disclaimer saying I'd been offered a repayment protection policy and had declined it.