There are so many competing systems because the problem of turning two numbers (a coordinate pair) into a string is trivial, so everyone comes up with their own

There are so many competing systems because the problem of turning two numbers (a coordinate pair) into a string is trivial, so everyone comes up with their own bikeshed. The individual details of the systems don't really matter. Sure, they each have some small advantage or disadvantage, and you can argue about them for a long time, but in the end, what matters is usage/adoption. A widespread but suboptimal system is better than a system with better properties that few people know/use, because the differences barely matter. Unfortunately, there isn't sufficient need for such a system that ordinary people would regularly come into contact with it, and any group of people that does have such a need already found a (proprietary) solution, so it's unlikely we'll get a standard soon unless big players agree on one and aggressively push for it.