I'm from the UK and we always use Metric. But I also learned how to use Imperial because... Why? I actually don't know why. My old math teacher was strange like that.
Metric is all like 1mm * 10 = 1cm, 1cm * 10 = 1dm, 1dm * 10 = 1m and on the other hand you got the Imperial being all like 1in = 2.54cm, 12in = 1ft, 3ft = 1yrd, 1760yrd = 1ml like wtf? How did someone come up with such a random thing?:/