Just to add to "excelone's" question, what is the real reason why a passenger with only carryon luggage is not allowed to disembark at a more convenient airport after a diversion due to weather or some other non "Tech" problem where immigration or customs are not an issue.
I have been on a flight that diverted to its final destination due to weather bypassing the enroute airport where the CC insisted that we all should remain onboard to fly back to the onroute airport due to "insurance reasons", this resulted in a couple of the passengers actually forcing the issue and insisting that they could disembark which in the end they did.