"Michael Black" wrote in message There is no expectation
that the voltage might come from a variety of

sources, in this case the power supply is external either because it was
easier to get UL approval with the external supply, or perhaps because the
supply might fail and it's easier to change the power supply if it's
external. So they picked the needed voltage in the first place.

Often the same electronic equipment is used in several countries. They all
have differnant kinds of power and plugs. It is easy to use a differant
external supply instead of building differant ones into the equipment.