When I canceled my insurance after going carless, I was told that there would be a lapse in my coverage causing my rates to increase. So naturally I asked why would I cover a car I no longer own. Apparently, there is a type of insurance that covers you as a driver of other cars. Of course there is. Going on 4.5 years now with no insurance payments. It's been glorious
If you do regularly drive other cars, it can make a lot of sense to make sure you have a liability policy that will cover an incident (vs assuming that the coverage on the vehicles is appropriate for you). Not sure why you'd be bothered/dismissive that you can access a sensible financial product.
It was less about me driving (I don't drive since going carless), but more about here's a way for us to keep you on a monthly payment for a service you no longer need to avoid "lapse in coverage". That's like telling someone they will have a lapse in their homeowner's coverage while they are renting.
Some credit cards like American Express offer their own insurance as part of the membership fee as long as you pay for the rental with their card, and decline the coverage offered by the rental car company.
This is typically (including in the case of AmEx) collision insurance only, not liability insurance. You still need liability insurance from somewhere.
There are companies that will sell you rental car insurance as a standalone policy. Google "Rental Car Insurance". Last I was dealing with this problem myself, the policies were something like half the cost of what the rental car place wanted.