I tried to track down the reasoning (I mean you would think a right-leaning pro-business president would support the Metric system), this came up:

https://themetricmaven.com/terminating-metric-with-extreme-p...

He did sign the Omnibus Trade and Competitiveness Act of 1988 into law. The measure declared that the metric system of measurement to be the preferred measurement system for U.S. trade and commerce.

But he also defunded the US Metric Board.

I suspect he didn't care about metric enough to fight other conservatives over it.