Honestly real reason that we still use the Imperial system is because (for most of us) the gains of using metric don’t really outweigh the annoyance of having to switch over from a system over which we already have a common understanding of. That is to say that we can instinctively understand how long a foot is since we are used to it, and it’s hard to reside you’re brain to reach that same level of understanding within a different system as an adult. I say this as somebody who works in a Biology lab and uses these measures daily.

Also there’s a good chance we’d end up with some half-baked system like in the UK—height measured in feet, length in meters, distance in miles, speed in kilometers, gas in liters, gas mileage in gallons, weight measured in stone(???).