The problem is - its what we are used to. UK is slowly going metric, taking forever and a day, but we are getting there. I lived in Germany for 14 years in the days of my youth, and all is divisible by ten/multiply by ten - its hugely simpler - weather, distance, temperature etc etc all links together logically.
If we were to have a clean sheet, and have the choice between the ones below
System A
Unit of measure based on 1 (inches), 12 (inches in a foot), 3 (feet in a yard), 1760 (yards in a mile), and the real doozy 6 (feet in a fathom)
System B
Unit of measure based on 1 (millimetre) , 10 (millimetres in a centimetre), 100 (centimetre in a Metre), 1000 (metres in a kilometre)
Its a bit of a no-brainer .... as for Hectares, acres, perches, rods, chains et al used inside a non metric system ..... arrrgh
Just dividing by ten (etc) is sooooo much simpler to achieve the same end.

Have a think about this one - why the hell are we using 60 seconds in a minute, 60 minutes in an hour, 24hrs in a day, and 365 days in a year (366 on leap years...). I reckon ET phoning home would have a field day explaining that one to his relatives
Regards
Zy