Don't parking/marker lights generally turn on your tail lights at the same brightness as when the headlights are on? Tail lights are generally two filament bulbs. The dimmer one is the continuously-on marker light and the brighter one is for the brakes. Maybe it's different with LED-native lights? I personally use just the marker lights in the rain (and dusk) because unless I am benefiting from the headlight beams, it's just extra light pollution for oncoming cars.