It's true that you don't see the spring-loaded tray or plate stacks as much, but it's an analogy that has stuck with us. We have a similar situation with "radio buttons" in graphical interfaces. The name is losing its meaning relative to actual radios over time, but the name is still here in a particular input type.

As far as the contents of the stack: all analogies break down sooner or later. The stack of plates is just a starting point. This is Perl, so that stack could contain plates, trays, scalars, turkeys, or small cars.