There are many taxes besides income tax. Consumption taxes tend to hit low income people hardest.
EDIT: s/income/sales
That only means at state level and most places will add taxes at a locality level. Consumption taxes in general are popular throughout the world not necessarily because they're optimal or something like that but because they are easiest to enforce and administrate compared to income taxes. Just look at our complex federal tax code for what can degenerate within 60 years. Now, with a VAT things are somewhere in the middle between sales taxes and income taxes and is subject to the same political pressures to shift around taxation toward "less desirable" activities as deemed by politicians.
Oregon (my own state) has no sales tax anywhere, including localities.'