we do! one inch is exactly 25.4 mm. fluid volumes are almost always seen in both standard measure and metric. most disposable plastic water bottles contain 500 mL of water. lots of engineering for american stuff is actually using metric measures too, including automobiles!

other places use the standard measure as well. in canada, you'll construct something with 2x4s and 4'x8' sheets of OSB. in the UK, oh goodness... it's a complete catastrophe. you'll see distances in kilometers but speeds in miles per hour, and don't even get started on stuff like body weight measured in stone, or the breakfast cup (these are actual, real units!)

a very good example is altitudes of aircraft. except for russia, china, and some ex-soviet nations, it will be in feet (or hundreds of feet; "flight level" 320 is 32 000 feet!). this holds true from the bahamas to japan to lithuania. the speed unit knot is a bit weirder, doesn't neatly fit into either boat (pun absolutely intended), and is worthy of its own write-up.

whatever units you use, really our main suggestions would be to follow in the footsteps of the SI (even if using non-SI/non-metric units), be clear, and be consistent!!

stay safe and happy measuring :)