I imagine that quite a lot of older drivers, who might otherwise have kept driving occasionally, have given up when faced with the medical questions that they face when applying to renew their licence.
As many on Gransnet have already discovered, the DVLA can keep coming back for more info, and then keep you on tenterhooks for many months waiting for their decision on whether or not they are going to approve your renewal.
Mind you, I strongly suspect from threads on the subject of licences that many of the people who say that they keep renewing their licence just so that they have ID must be selective with the truth about their medical conditions on their applications. And if someone has that licence and still has access to a car, you can bet that some of them (though hopefully very very few!) will still be tempted to drive sometimes!