Because rates in the UK without CDW included tend to be very expensive. It is cheaper to rent a car with CDW included ( with an excess of around GBP600 ) than not to have it at all

If you didnt have CDW, I doubt that there are any travel insurance policies which would cover the entire value of the car

For UK, I would tend to think of it in the same way as Australia rates all include CDW ( albeit with excess of 2k to 3k ) and not easy ( possible ?) to get a car with no coverage at all

The rate I mentioned doesn't include the scam excess reduction options which would reduce the excess

Dave