The one I use also doubles as a savings plan (not much but better than nothing) but is not an insurance for permanent income replacement.
It's all a gamble - I was offered critical life cover for my mortgage once - I was in my late thirties and super fit, couldn't see any point in the extra expense, I ate healthily went to the gym three times a week and cycled 150 miles every week. Couple of years later I got cancer
.
Problem with this job is any accidents or illness and you're stuffed if you work alone. You can go from £1000 a week to £0 per week very very easily.
Of course there are some guys who abuse the system already - you know the ones, bragging about their incomes, finishing by two thirty, starting at ten thirty who already rip their income from the state. 'Lifestyle choice' is the term they use. Loss of income for them would probably make little difference.