It would be a very unusual driver who rents a car without having driven one for a couple of days, let alone 6 months to a year.
I have never been to Boulder, but I lived in London for 5 years without a car at all. It makes no real sense to have one in London and is much cheaper to rent a car when needed, I would bet that is true of places like Tokyo as well. Whilst your observation is maybe true for much of the US it is not quite as cut and dried elsewhere. Anyway I meant it to serve as an illustration. The rental company have no knowledge of your driving activity and are in the same position as the dive op.
What is your view on it? Would you lend your own car to a friend that hadn't driven for a year (maybe in prison for example - I hope none of your friends are - but it is another example)
Would you rent me a left hand drive auto when I normally drive a right hand shift?
Very interesting point chrisch. I do live in Tokyo and like you in London, I would not dream of driving every day here. This is a city where perhaps 80%+ of the time it is faster to go by train/subway than car/taxi if you know your way around. But as far as driving goes I do drive occasionally (2-3 weekends a year) in Japan if I need to go into the countryside and I rent a fair number of times a year during international travel but certainly no where near every day or even every month for that matter. In driving a car perhaps I don't feel like I get rusty but I used to drive every day for 15 years, anything forgotten is back by the time I get off the rental lot. I'm also equally as adept in left hand or right hand drive and manual transmission on either side (grew up in the US, lived in country driving on left for 5 years and holidayed in countries driving on the left more often than on the right). I certainly don't feel guilty for renting a car, left or right hand drive when I travel nor do I feel dangerous to myself or others. I have yet, in perhaps 150-200 rental cars, to damage one.
In the end, it's a great point of where extensive past experience can easily make up for recent occasional practice and mandatory refresher could be overkill after a short break.