The better question to ask is what is the benefit? For everyday usage by regular people, it's not clear to me that metric is superior if you didn't grow up with one or the other, hence the lack of push for a change.
In fact, I've seen the argument made that feet, inches, miles, cups, teaspoon, Fahrenheit, etc are superior to meters, centimeters, km, mL, Celsius, etc for everyday use. As I've seen it presented, this argument contends that centimeters are too small, while meters are too large for many common things you want to measure, such as the height of a person. Likewise cups and teaspoons are actual objects that you could visualize and get a general sense of the amount without even knowing the actual measurement. Same kind of thing for Celsius: the most common usage of temperature measurement for the average person is air temperature. For the set of air temperatures commonly experienced on Earth, Fahrenheit provides more precision.