Positive and Negative cable colors?

[Stangfire]

Hi, I'm new to the travel trailer world.

I'm curious why the battery cable connections are not standard RED POSITIVE and BLACK NEGATIVE like all automotive 12 volt systems.

Thankfully there is a tag that tells me which way to hook them up and I can see that the white wire goes to ground.

Is there a reason for this? If I know the reason maybe it will be easier to remember.

Thanks.