No, you're absolutely right. Thing is, most of the time, when dealing with miles, I don't care how many feet it is. Any distance measured in miles is sufficiently large that its equivalent in feet is largely irrelevant. I suppose it's nice to know that 1.73 km is 1730 meters, but either way, it's a medium-long walk. If I needed to convert all the time ( I suspect this it's really only when using compound units like pound-feet ), that is where I find metric more useful.
Also, I haven't read GP's post, but I find Fahrenheit degrees easier to work with primarily because they're smaller; differences in temperature are easier to express in whole numbers.
Gallons, cups, tablespoons, quarts can go DIAF; I have to convert between these all the time, and it drives me batty!