Yes in modern times we put pop culture figures on stamps but in the 19th and early 20th centuries only really significant people imagery or events qualified for memorial on stamps, coins or currency.
I don’t really have a problem with notable people or causes in general, or historic artwork, being put on postage stamps - or holidays celebrated.
I think the currency should be reserved for those who have done valuable, historic service to the Nation - presidents, military, even astronauts.
But not actors; unless one should have somehow become president :-)