I’m not a medic at all, but would guess that since alcohol tends to liquefy blood, it could explain why you bruise when you’ve been drinking. It’s also the reason why it’s better to not drink alcohol the day before getting a tattoo, as you’ll bleed more.
Now, with the inverse reasoning, maybe you don’t bruise because your blood is “too thick”, whatever that could mean? Maybe ask a physician ?
As a European: we got the latch.