Why not use higher voltage, like 24 or 48V?

That's how it came, and while I've incrementally added or replaced a lot of things there's no point switching.

I would probably go with 24V if starting from scratch - there's a huge market of automotive and caravan parts that are 12/24V and generally don't support 48V.

If relying on an inverter more I might have a 48V main bank and run the low-voltage stuff off a DC-DC.