Fahrenheit gives a better range of usable temperatures than Celcius. "It's in the 60s" vs. "It's in the 50s", etc. There's no scientific reason for using Celcius instead of Fahrenheit, either. Unless you are boiling water on a day to day basis, there's really no excuse not to be using Kelvin for everything.
Up north, it's very convenient to be able to look at the sign of the temperature to determine whether there's a risk of ice or snow on the road. Also, how are you supposed to make tea (or coffee, if that's what you prefer) without boiling water? That said, the Celsius scale is not very well integrated into SI.
Likewise, the fuckers could have kept one Imperial units for distance, etc., and simply tacked base-10 onto it (kiloyards, centiyards) instead replacing them with arbitrary units like meters and saddling us with a secondary measurement system that is no more scientific in terms of the base unit than the Imperial.
From a European point of view, the question is which unit to use. Before the metric system, there were, for example, literally dozens of different feet. The yard differs from the metre by less than some of these different feet differ. Also, there are still several different gallons in use. Surely it's better to give the common unit a new name rather than call it a "yard" and confuse everyone.
All you metric purists that aren't using lightseconds and Kelvin, should really check your sense of superiority at the door.
A foot is roughly one light-nanosecond, right?