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.

Speaking of DC though: The EU is looking into applying HVDC not just to point-to-point connections but at a network level. Don’t expect that to hit your home in your lifetime, but if you’re an aluminium smelter it would make a lot of sense to have a direct connection to tons of DC.