petrol is one of the few things we buy that has tax built in. you pump $23.72, that's exactly what you pay. You prepay with cash - you're having to estimate what, say, $15 will get you. Delta of $2.80/gal vs $3.30/gal - yeah, it's a bit different, but nothing is hidden.

Sales tax on literally everything is fairly different state to state (and within sometimes) but petrol is a major daily thing that is tax inclusive.