I'm as much a defender of SAE as anyone. Metric is better for counting when you only have your fingers and toes to do it with, but most engineering and construction applications involve dividing a large object or a long distance into smaller ones, and for that SAE works better, simply because the human mind is better at dividing things into even halves (and, by a quirk of the integer system, into thirds) without using any measuring tools, than it is at dividing things into even fifths (which the decimal system would require).

In NASA's case, though, they really shouldn't be relying on "eyeball approximations" for anything. SAE is best for work in the field, where nothing ever quite fits together perfectly and unless you do a lot of approximating you'll never get anything done, while metric is best for when everything absolutely MUST fit together to a precise level of accuracy. This is generally of most use for scientific experiments in the carefully controlled environment of a lab, but in extremely dangerous environments like space, where a fraction of a millimeter can mean the difference between landing safely and burning up on re-entry, it's also pretty important.