Most software IT/ops is luckily generally much smaller in time scale of most incidents, and much more tolerant of hand-off errors and delays. Ex: For 24/7, you get an instant email acknowledgement of ticket receipt, someone triages it, and if on a boundary, OK for current shift to ignore and leave for the next one. Likewise, for bigger incidents, better for throughput for the same person to pick across shifts to avoid hand-off errors, even if that introduces delays when it spans shifts. But not universally true across orgs, nor for incident types. Ex: For tricky & sensitive incidents that take 8-24 hours, the hospital results show longer shifts might make sense, so I'd want to see experiments before making assumptions!
Three shifts works well for 24/5, each shift running eight hours a day.
Blind men and elaphant? :)