For the vast majority of the population there’s very little advantage to using either system. Even in a fair number of technical fields there’s limited advantage in using metric until you’re doing actual chemistry or physics, and anyone doing that learns metric easy enough anyway.

This isn’t saying metric is worse - it’s just that for most people neither metric nor imperial (yeah yeah I know, “US customary units”) offers any significant benefit over the other.

So when you have 300 million+ people who are all accustomed to imperial, with all their plumbing built using imperial pipes and fasteners, with every structure in the country built in imperial units, with every road sign in miles, every thermostat in Fahrenheit, etc etc you’ve got to have a compelling reason to move them to the new system.

The UK had this with their membership to the EU that pushed them much more towards regulatory compliance with the europe (EEC I tHink it was before the EU) but the US didn’t.

The government formally adopted the metric system decades ago, but initial efforts to get the population to switch fell flat and since then there’s not been the will or need to force a switch.