Cling onto that raft! I fear it's a combination of NIH (despite the same being said of imperial, Fahrenheit, etc), fear of change, and irrational dislike of the French. Of course, Daniel Fahrenheit was Dutch/German, and Anders Celsius was Swedish.

But if you think kg is frustrating, I'm learning electronics now - every book, when starting to talk about capacitors, says something like 'However, the Farad is not a convenient unit, and you'll most be working with 0.0000000001F capacitors'. Yes, the SI unit is unhindered by a prefix, but you can't but help wish they'd thought more carefully about this before writing it down.