"Except in the United States".

Would you like to try and convince a third of a billion people to change how they measure everything? In a system where getting in power means winning a popularity contest, anyone that tries to pull a sudden change like that isn't going to get far. I agree, metric is so much easier, but a change isn't as easy as it sounds.

Because American scientist are all secretly hipsters and the metric system is too mainstream.

In Physics class we used exclusively Metric.