Germany has been completely metricated for so long that several pre-metrication generations are no longer alive. Yet some Germans are still using customary units. And that's fine because they are simple multiples of metric units and are the same everywhere in Europe. For example a pound - to the extent that it's still in use - is nowadays exactly 1/2 kg except on those islands in the North West.
What most people are really attached to is words, not the precise size of a unit. What they don't understand is that with metrication they don't have to give up these words. They can call 1/2 kg a pound, they can call 1/2 litre a pint, they can call 1 metre a yard (this is already in use for distances on British motorways), they can call 1.5 km a mile. Years ago my mother sometimes asked me to bring half a pound (= 1/4 kg = 250 g) of butter from the supermarket. You can go down to the pub for a metric pint of 0.5 litres. Sure it's a bit less than an imperial pint, but you will get over it. Maybe see it this way: It will be a bit easier to have two. Or even three. This will be similar to what happened in Bavaria. A "Maß" of beer (e.g. at Oktoberfest) was once 1.069 litres. Nowadays it is precisely 1 litre.
Incidentally, every German child still knows some of the units as they still occur in fairy tales and other old texts, e.g. "7-mile-boots". They just don't know how much these old units are precisely, and as these formerly were different in different parts of the country, there isn't a simple answer anyway.