> The task of representing a pair of numbers is trivial
The task of representing a pair of numbers is also not what any of these systems do.
"Two numbers" work because they're taken from an infinite set. Longitude lines are not parallel. Near the poles, moving a degree is only a few inches, while near the equator it is miles. This works for latitude and longitude, because these numbers are taken from the infinite set of real numbers between 0 and 180--if you want to represent more precision near the equator, you just add more digits on after the decimal point, and if you want to represent less precision near the poles, you just ignore the excess digits. In practice, on computers, they're represented as doubles, which have enough precision that we don't need to care that they aren't reals.
However, if you're mapping into a finite set, this falls apart quickly. The finite set for W3W is the set of permutations of 3 words taken with replacement from a set of 40,000 words. This gives them 40,000^3 combinations, which means they can represent points about 9 feet apart all over the world if they distribute these points fairly uniformly. But if they just trivially convert them from latitude and longitude, they won't be uniformly distributed--they'll be distributed tightly packed at the poles, and distributed loosely packed near the equator. This means your locations won't give much precision near the equator (where more people live) and will be more precise than GPS can measure near the poles (where almost nobody lives).
You can add more precision at the equator by adding more words to your word list, but it's already 40,000 words, which is more than humans can reasonably check, which is why there are a lot of homophones and sound-alikes in the list. You could also add more precision at the equator by adding more words, but it's obviously more desirable to say, "elephant.cheese.traffic" than "elephant.cheese.traffic.indigo.query.crenelation.trample". It would be much better if we could take some of the points we mapped to the poles, where we've got way more precision than we need, and put those points near the equator, where we don't have enough precision.
So now you're looking at the mathematical problem of packing points on a sphere[1]. It's not a solved problem, but there are good enough approximations (and "representing a pair of numbers" is not one of them).
The task of representing a pair of numbers is also not what any of these systems do.
"Two numbers" work because they're taken from an infinite set. Longitude lines are not parallel. Near the poles, moving a degree is only a few inches, while near the equator it is miles. This works for latitude and longitude, because these numbers are taken from the infinite set of real numbers between 0 and 180--if you want to represent more precision near the equator, you just add more digits on after the decimal point, and if you want to represent less precision near the poles, you just ignore the excess digits. In practice, on computers, they're represented as doubles, which have enough precision that we don't need to care that they aren't reals.
However, if you're mapping into a finite set, this falls apart quickly. The finite set for W3W is the set of permutations of 3 words taken with replacement from a set of 40,000 words. This gives them 40,000^3 combinations, which means they can represent points about 9 feet apart all over the world if they distribute these points fairly uniformly. But if they just trivially convert them from latitude and longitude, they won't be uniformly distributed--they'll be distributed tightly packed at the poles, and distributed loosely packed near the equator. This means your locations won't give much precision near the equator (where more people live) and will be more precise than GPS can measure near the poles (where almost nobody lives).
You can add more precision at the equator by adding more words to your word list, but it's already 40,000 words, which is more than humans can reasonably check, which is why there are a lot of homophones and sound-alikes in the list. You could also add more precision at the equator by adding more words, but it's obviously more desirable to say, "elephant.cheese.traffic" than "elephant.cheese.traffic.indigo.query.crenelation.trample". It would be much better if we could take some of the points we mapped to the poles, where we've got way more precision than we need, and put those points near the equator, where we don't have enough precision.
So now you're looking at the mathematical problem of packing points on a sphere[1]. It's not a solved problem, but there are good enough approximations (and "representing a pair of numbers" is not one of them).
[1] https://stackoverflow.com/questions/9600801/evenly-distribut...