I am truly and sincerely sorry if my post uspet you Charleygirl- and I do hope you will realise that it was NOT PERSONAL- and that my post had a big IF in it.
Having been through this with both my parents- my dad didn't have MC but he drove until he was 94- for exactly the reasons you stated, eg living our in a rural area, and also because my mum became blind (a combination of MC and glaucoma) a few years after her car accident, the last time she drove. Dad also wrote his car off and ended up in a lamp-post- neighbours phoned me in the UK and said all in the village were concerned that he really should not be driving anymore- and it was a miracle no-one was hurt. I talked to him on the phone- and the next day neighbour phoned to say he'd bought a new car, much more powerful than the previous one... It just wouldn't listen to anyone.
In the end, the GP and police visited and told him to give his keys up to them- and he blamed me and my neighbour for interfering. I've sworn to our daughters that if they ever feel the time has come, we would agree to go for full visual and medical + driving skills assessment- and act upon the advice. We have chosen to live near a rural bus stop with excellent service- and swore we would get used to use it if ever necessary. I suffered too much worrying like crazy about my parents' dangerous driving to ever inflict that on my own children.