Lets forget about the "get prosecuted" bit and the CAA attitude.
Why do very experienced pilots take risks with fuel?
I would suggest that we should never plan a flight (even in the circuit) that would leave us with less than 1 hour fuel after our planned alternate.
We had a fly-in some years ago and an aircraft had a heavy landing and damaged it's landing gear. The runway was blocked for over 1 hour and a few a/c had to divert. (the nearest being 40 miles).
A C152 landed at the alternate and when the pilot filled the a/c he put the exact amount of total useable fuel in the tank. He admitted to me that he thought the engine was going to stop when turning final but was ok when he levelled the wings.
He will never do that again, but why does it take such an experience to make pilots take note of the danger?
In Europe we buy fuel in litres and we should calculate in litres, (in the USA, use gallons) no need to convert anything. Pilots only confuse themselves, nothing to do with the FAA or CAA
Tony