It's not obvious because it's unlike any other commonly used recreational drug. Alcohol at typical dose has zero-order pharmacokinetics, unlike most other drugs

It's not obvious because it's unlike any other commonly used recreational drug. Alcohol at typical dose has zero-order pharmacokinetics, unlike most other drugs which have a half-life. This can result in surprising differences in intoxication with only small differences in intake per unit time, as the article explains.