Of course, you are in the UK, not the USA.
Metric is very silly in day to day terms, as you clearly shown by lapsing into hundreds with your two examples. The arbitrary nature of the metre means none of the measures are practical in day to day life. A litre is to big for beer, too small for petrol. A centimetre to small for judging or measuring a persons height etc. A kilogramme too large for recipes and the gramme too small for most dey to day purposes.
.
My point, though, was that we are in a massively connected world. In a particular instance you might feel confident in making an assumption but if you pick an arbitrary document (in English) which refers to pints, you cannot safely do so.
Hundreds and larger numbers are in pretty darned regular daily use with many units!
110 yards, 220 yards, etc. were standard athletics distances.
200 pounds is a pretty regular US expression of someone's weight.
London to Edinburgh is around 400 miles.
Mountain heights in feet.
Flying heights of aeroplanes.
Grosses of matches.
Daffodil heads.
A litre for petrol measure is just fine. Gallons were a pain as you'd so often end up with halves and quarters. Whereas a typical car of today having a tank of around 50 litres means that to the nearest litre is perfectly acceptable most of the time. Much easier than working out things like 8 3/8 gallons at 6/10 a gallon.
A kilogram of flour is just right for my bread sessions. With three to five grams of a special yeast-like ingredient. Certainly wouldn't want to deal with fractions of ounces. Or 46/7000 of a pound (grains).
In the end, almost everything is arbitrary when it comes to units. And a reasonably consistent system more than makes up for sometimes larger numbers and complexity of other systems. Indeed, avoidance of fractions alone is a major help.