You see, units of length like feet or inches and yards are like units of small weight in that they 'belong' to tradesmen and builders while units of distance like miles and large weights or the weight of precious metals belong to kings. Traditionally, the smaller units are based on the human body (e.g., the inch is the width of the average thumb) while larger ones measure how much distance a phalanx of troops must cover (the mile is one thousand paces.)
Later, scientists invented means of measuring air pressure, temperature and electrical current. About two hundred years ago, French scientists got together and decided to replace the national standards of Europe with what they thought of as a rational system based on decimal multiples of units instead of dividing by halves or twelfths. The one thing that they didn't bring into the fold when they created the metric system is units of time. Oh, they tried a new calendar for a while but it didn't take for one good reason: they couldn't really suppress Catholicism so the Catholic calendar and its sub-units stayed.
This is because like all calendars, the one we use now was put together for the convenience of the people we allow to 'own' the hours and days: religious leaders. Priests and shamans and the like have been in charge of time for so long, we tend to forget that they've been calling the shots since they promised that they could make the Sky Wolf cough up the Sun Maiden every time an eclipse took place. If someone rational were to come up with something, you'd get what I'm going to lay on you tomorrow. If you get jerks like the Pattersons doing it, it would make the odd habit of a twenty-eight day month because dead people hated even numbers seem sensible. More on that the day after tomorrow.