Why does the US use the Customary measurements instead of metric?
1) Most Americans see no reason or advantage, in adopting the metric system.
2) They are comfortable, using US Customary measures (USC).
3) That is what they learned as children, and used as adults, and continue to do so.
4) Because USC has been learnt from a young age, its difficult to, "unlearn it", and learn the metric system. Conversion from metric back to USC, cause errors and roundings, which can be to course, or to accurate.
5) Its difficult to use metric, when everyone around you is using USC.
6) There is perception that the US, is world leader, and others should follow its standards.
7) There is a perception that metric is foreign, and therefore inferior and evil.
8) There is a perception that converting to metric, would be very costly, and offer minimal advantages compared with USC.
9) There is no political will, direction, or plan to adopt the metric system.
I hope this answers your question.