Your reasons listed under a HN comment are more plausible than those listed by who worked on this subject for years. I find it funny and admiring.
replyTaxi drivers and ambulance drivers seem like two jobs that would have less regular sleep patterns, TBH.
replyThat's what I was possibly thinking as well. Or it could be that their jobs are stimulating in a way that makes them tired in a way that promotes quality sleep.
replyOr maybe they just get great at napping on the job !