If you go back to the physics of electricity, its the flow of electrons, and there are electrons on both sides of the switch and even in the fingers that will flip the switch.
The switch opens a path for them to move while the battery provides the push to get them moving.
Electrons are kind of like teenage children.
They have lots of potential energy, but nothing happens until they are pushed or motivated. In the old days that motivation was sometimes provided by a switch. These days its common to bribe them with technology or other stuff instead.
Three guesses what my problems are there days...
