I don't know the distribution of people using left or right across the world and how it is determined. It might be even close to 50% everywhere in early infancy, but once one "main direction" emerged at society level (by luck - like there were 4 people writing in that direction versus 2 in the other), maybe everybody is "pushed" in that direction.

Anyhow it's a matter of trade-offs and each society ended up with different ones - I mean direction I find least controversial, think of Chinese and Ancient Egyptian scripts that are logographic - why did they end up with that?

We can also analyze if some convention makes sense or not and why, even if the initial decision was taken for the "wrong" (or some irrational) reasons (ex: the village priest heard a voice).

Yes, I think there are many interesting things to consider about maps (like projection, orientation maps fixed on a panel/wall, orientation for digital maps). All those discussion will also transmit the basic idea (there is no "good/bad" way) while also discussing other problems ("can't represent area well", "people like different options", "different cases require different orientation").

I think might have more to do with the ink getting wiped/mangled when the first books were written. Even today, if I would be to fill a page bottom to up while writing with an ink pen, I would probably make some mess of the text already written.

Same reason for writing left to right probably (given someone that writes with the right, but that seems to be more common).

> An "upside down" map is just as valid as a right side up map.

Is it as useful and/or efficient though? I could write a phrase in English from right to left and if you really wanted you could read it, but it would be highly inefficient.

An efficient society sometimes has to pick conventions (how to write text, how to print a map, what characters to use, etc) and I find not interesting to point that other conventions could have been used.