For good or ill, things that were once commonplace turn into anachronisms. Such is the way of the world, there's little point in railing against it. I know folks that haven't worn a watch in decades, they prefer to rely on their mobile phone for the time. I don't feel properly dressed without a watch, but I couldn't care whether it's analogue or digital. Due to my background, I also have a nasty tendency to use the 24 hour clock. Telling someone that it's 18:45 seems to confuse the hell out of many people, regardless of their age.
I was never formally taught any Imperial measurements. Any knowledge I have of them comes from fishing or working with old "legacy" equipment or American sourced stuff. I know the names of pre-decimal coinage, but have no idea how many pennies make up a shilling, or shillings a pound.
I'd expect the vast majority of folks under 48 (ish. Those that were the first to do GCSEs) to have even less knowledge of Imperial measurements and pre-decimal money than I do. There's not much need for them to have such knowledge and most will not have been formally taught about either much beyond them being footnotes to a text.