I prefer metric to imperial, but if milk changes from pints to litres, it's probably for shrinkflation since they can shrink the bottle from 2.272L to 2L and most people won't notice.
That's exactly what happened with beer. Newky Brown was the last hold out, now even they do 500ml bottles. Some cider still has pints, but I think even they've dropped down.
I always assumed guys measured in imperial because metric is numerically smaller. That may be one reason some people don’t want to switch to metric, now I think about it.
As much as I dislike imperial, I'm still used to using Fahrenheit for body temperature. 99 mild fever, but you still have to go to school. 100 stay at home. 103+ you're dying.
In Canada speed is always kilometres. For distance we don’t really use miles for jogging but most know the conversion if they are avid runners the rest the same. For temperatures it’s Celsius but people in border towns may use Fahrenheit. For weight for people official documents will be kilograms but most people talk in pounds, no stones. For measuring it can be both metric or imperial ie cups. For liquids it always in metric so millilitres or litres but if you go to the pub you can order pints which people think of in ounces and depending on the pub could be 14-20oz.