As odd as they seem, Empirical units are very practical for the purposes which they served. They were quite useful to the people that used them, at the time they were used. If they weren't useful, they wouldn't have been used.
They were also not all used by the same people, for the same purpose. People who measure in points and picas are not going to use nautical miles for measuring the same things. For those same reasons, the relationship between the two units, although it can be defined, is irrelevant and useless.
