Right. Essentially, before the Enlightenment systems of weights and measures didn't exist in the standardized way we know it today—measurements traceable to national/international standards, etc.
That's not to say local standards—let's call them weights and measures—weren't strictly adhered to and enforced. They were. There are many recorded instances from history to illustrate the point from, say, Archimedes' eureka moment to that of the obsessive and overzealous Issac Newton† when Warden of the Royal Mint was roaming around London checking for clipped coins and bringing the perpetrators to justice.
I'm fiercely pro-metric, and I've had much to say on the matter on HN over the years. So I'm used to the guns coming out from those in the US defending the Imperial system. I've good reason, at school I learned the Imperial system, CGS and MKS (it was before SI). In say physics learning to do things fluently in three different systems was a recipe for mistakes and confusion.
At the risk of repeating myself (link below), learning foot poundals, dynes and Newtons was bad enough but to have to convert between them in exams really was pretty rotten. The other reasons I've also menrioned, I've sat on standards committees and have writtern standards (nothing as illustrious as the ISO but it was for an intergovernmental organization nonetheless). Writing standards is often a tedious thankless task (I don't have to tell you people don't read them for the fun of it).
The link below is me getting worked up on HN over the metric system over a number of rolling posts, and it's not the first. I've referred to it here more for the sake of completeness than anything else. (I don't like rereading my old posts so I don't expect others to do so.)
https://news.ycombinator.com/context?id=43880977
† Newton. Not exactly weights and measures but a well documented case: https://coinsandhistoryfoundation.org/2021/04/30/sir-isaac-n...