What happens if you don't pay? The consequences are aggression, and the fact that threat is hanging over you makes taxes a form of aggression. Coercing is a form of aggression.
You get charged interest. Then, you might have your wages garnished. If that isn't sufficient, your bank accounts might get frozen. If that still isn't sufficient, liens.
Note the 'almost'. I'm sure some outliers exist but that's not what we're talking about.