Yep, DH had to convert to mm when submitting plans for a garage, a few years back.
The stubborn adherence to imperial for anything quilting related is down to it having strong American roots, even though other quilting traditions are available. Naturally, this spills over into bag making and a lot of dressmaking, though my Japanese machines have the metric measurements more prominently marked on the stitch plate than imperial ones.
I suspect that most of us over the age of about 50 readily toggle between. Not Fahrenheit, though. That is nonsensical and can get in the bin.