Yorks ppl
Sorry the attempt at humour fell flat. I agree that a failure to the hot air position would be preferable to the cold however in my experience that is not the way the things are designed.
We've had reliable fuel injection in cars for donkeys years, which gets rid of the problem entirely, but then if I were driving a 57 year old car instead of a 57 year old aeroplane I wouldn't have it on that either.
All engines are different. For example the small Continentals have all of their inlet manifolding hanging out in the breeze, making them more susceptible to carb icing while the Lycomings tend to have it embedded in the sump where it gets warmed by the oil.
While the RAF ran their Chippies on permanent hot air they no doubt also factored the result into their take-off calculations. Running other engines on permanent hot air might not be a good idea because it causes them to run rich and, as a result, cooler, making them not only less efficient but also increasing fuel consumption and the environmental impact.
There are a number of situations after take-off where inability to achieve full power could be an issue, for example clearing obstacles following an enforced go-around or countering down-drafts in the lee of hills. However the likelyhood of that happening on a flight where the carb heat control failed after the pre-take-off checks is insignificant enough for me not to worry about it.
Mike