It was once upon a time, in the age of olde, where switched-mode power supplies were not the norm and GaN semiconductors weren’t in the process of taking over the whole power IC market. Taking in any mains voltage/frequency and spitting out any reasonable DC voltage is no issue for those things, they simply don’t care.
It’s still going to be an issue in the future but pretty much only for resistive heaters (well, at least the voltage part) and motors with oomph.