Sidelights (standlicht) are NOT the same as parking lights.
Though they may double as parking lights ...
This discussion refers to ancient, archaic legislation that was never updated and is not enforced at all .
You'll see very, very few -if any at all- parked cars using parking lights.
A parking light serves to indicate the presence of a parked vehicle
These were originally situated near the middle of the vehicle's side(s)
i've had a hard time even finding one ... on a really old oldtimer (Renault Dauphine 1947-61 !)
Modern cars no longer have actual parking lights
Another light on the car may be used (serve double duty) as a parking light - like the sidelights (standlicht)
If they have a parking light at all ...
Some brands can have a parking light enabled by leaving the indicator lever pointing to the side where you want the parking light to be on (you may need to do that after shutting down), then they switch on only that side's sidelight / standlicht
I've never even owned a car with a parking light function ...
Though it could be programmed in on at least one (i.e. it was not even enabled as standard)
It's an obvious drain on the battery
Especially if you have to leave on "standlicht" (sidelights) - let alone the foglights- your car most probably won't start the next morning
Parking lights may only be used in built up areas, outside these, you have to use "standlicht" / sidelights anyways
You can also see the silliness of the old legislation.
It applies everywhere on the public road, not just on the roadway .
You have to use a parking or side light when the car is not visible from about 100 when illuminated by public lighting ... so, even on an unlit parking or beside (not on) the roadway in a designated parking area
With modern paid parking buildings (yes, they are seen as public road !) shutting down the lights when no-one is present, your car would need to have its (parking) lights on while parked there...
A lot gets added to traffic legislation, but few outdated things are ever taken out again ...