3 4 5 works for metric ad well
Well, yes, it does, @chomalungma - but in practical terms, when you're using Pythagoras in the absence of a set square, feet are a more practical, reliable and, importantly, memorable, measurement than metres or multiples of mm.
Unless you're in a kitchen working with length and depth, then multiples of 60 (with a tolerance) are more likely to be the most often used unit. Or as I call them, appliances - 'you need two appliances plus a bit on that side' - 1500mm on the plans. People can visualise two appliances, but not one thousand and five hundred millimetres. Of course, the measures come out at that point, but the initial reckoning is easier.
Metric (or SI) units are best for theory or something that is extremely precise/extreme size, whether very large or very small. But Imperial came about for practical applications.
Having said that, as with the Appliance reckoning, most of my recipes are in blobs, glugs, slugs and half pans/packs. It's only baking where the scales come out.
Being able to switch units is far more useful - as then you aren't caught out by something being made in a non standard measurement, such as anything over a certain age, or tools in a different system than you've learned.