The early pioneers of this type of insurance where actually medical people not insurance people. They noticed that patients who they were treating for serious illness, such as heart conditions or cancers, were often experiencing financial hardship. And this was pouring fuel onto the fire, as it were.

Ironically, dying typically caused less of a financial problem and was therefore less of a financial risk. This is because many people tended to have life assurance, so their dependents had money and provision for the breadwinner dying. 

Secondly, for a couple, one of them dying reduced the bills for the survivor, who now had lower expenses. In addition, some people suffering a serious illness were facing significant medical bills or would benefit from having private treatment. 

These medics therefore wanted to create an insurance that could help with the financial hardship caused by a critical illness and were the architects of the first critical illness policies. 

For nearly everyone, of any age, in the UK today, their prospects of suffering a critical illness are higher than they are of dying during the mortgage term. 

In terms of a mortgage, you are more likely to need financial support for this serious illness risk, than your dependents are if you die.