nothing to do with speed (uk is much faster),
combination of driving without due care, lack of good driving Etiquette,
lack of police enforcement ( unless you are doing 73 kmph on a dual carriageway (50kmph limit) and stupid ticket along with it, while further down the same road, speed limit is 70kmph of standard single lane rd,
hk driving standard way too easy to pass and simple (should make it as hard as uk one)
and occasion driving like a mainlander with mainlander plates
tailgating is very common and dangerous
meaning that you have employ defensive driving techniques all the time