In commercial work or resi where the power source for the circuit is at the fixture (vs the switch) the conductors going down to the switch are called (drumroll please) switch legs.
In general, these are the ONLY time you can ordinarily expect to see a white wire used for anything other than (neutral) the ungrounded.
This is one of those "get used to it" things. Sorry about that.
The reason this practice is tolerated is mostly about money.
A good practice is to mark these non ordinary use conductors with some phase tape (some color OTHER than what is elsewise found in that box eg orange or yellow).
