There are special rules for labelling for alcohol given the obvious risks of consuming more than you realised.

Here alcohol must show the percentage alcohol content, but alcohol designed to be consumed as-is (without mixing) also states the number of standard drinks.

The number of standard drinks is the same as the “amount of alcohol” you mentioned.

Other ingredients like sugar aren’t shown as a percentage because manufacturers don’t want to show it, and it’s not required by law because although there are risks of excess consumption, they’re not “immediate risk to life” type risks.

Or you know… pay for things with your card?