As more than one person has pointed out, it would be switching from one totally arbitrary measurement system to yet another totally arbitrary measurement system. Not a lot of point, there. (Especially since we tried it in the 70s and it was vehemently rejected by the public.)
There are even societal reasons not to switch; some have observed that switching to metric also makes people less able to 'do' fractions. Or, apparently, use other systems.
It's especially amusing to go on a Jag forum and see all the metrickers moan about not comprehending a simple set of fractional-sized tools. The moaning gets really bad when you throw the Whitworth system in. Meanwhile the SAE/Imperialists grouse a little but keep going, because for them metric is easy and they've learned it after the slightly more complex system (of which Whitworth is a subset).
I can easily work in Imperial, SAE (which is different when you get to fluid measures), Whitworth and Metric. The continental Europeans I've worked alongside over the years often have had major issues wrapping their heads around anything that isn't metric.
Trivia: Whitworth is still alive and well and being used in consumer products. Millions upon millions of Whitworth fasteners are churned out every year by otherwise "metric" producers. Not going away any time soon. What is it used in? Camera tripod/accessory/baseplate mounts. The thread is 1/4" Whitworth.