I suspect most people tip on the after-tax amount when they calculate it themselves. I get that you don’t. I also know people who tip on the non-alcohol amount. Personally, I have always tipped post-tax.

These are also low-margin businesses. A post-tax surcharge keeps your overall bill lower than if they had raised prices, which would also raise the tax amount. The high labor costs are going to be passed on to consumers regardless. The surcharge shorts the government (which most of us are probably fine with).