That's a v-e-r-y interesting question which I can't answer! At first I thought, well, perhaps some AUs touch on *something* in canon, but even if that was true - and I don't think it is - it wouldn't explain *why* we find Bodie and Doyle in certain situations e.g. a circus context, in outer space, birdwatchers in Cornwall, i.e. contexts which have nothing to do with the world of Ci5 and yet we don't find the QAF characters in similar circumstances. An off-the-cuff suggestion, but maybe it's to do with their personalities and characteristics in canon? Tough, physical men like B & D might inspire tough, challenging situations, unlike the world inhabited by the QAF characters.