There is a big difference between GA aircraft which generally have DC nav lights, able to be powered by the battery, and transport category aircraft which have AC nav lights generally not able to be powered by the battery.
GA aircraft are normally electrically unpowered until engine start as you want to save the batteries. Transport aircraft are normally electrically powered the majority of the time even when parked up for some hours, only switching off when being put to bed for the night.
Then there is the tiger moth I used to fly which solved the problem by having no nav lights at all 😆😆😆
Thanks for all the responses... sounds like it is the industry norm, at least to a degree!