It is because sales tax is highly irregular, highly local, and changes often without any coordination across the multiple entities that can impose sales taxes. Manufacturers control published pricing for their products in advertising, physically on the container, etc. They are not subject to these local retail taxes, which can change the price >10% between locales.
This discrepancy is intrinsic to the fact that manufacturers set and advertise prices and then local governments effectively modify those prices unilaterally. At some point the customer will have to contend with the reality that the price at the manufacturer and the price at checkout don't match and control of that is spread across many organizations.
This discrepancy is intrinsic to the fact that manufacturers set and advertise prices and then local governments effectively modify those prices unilaterally. At some point the customer will have to contend with the reality that the price at the manufacturer and the price at checkout don't match and control of that is spread across many organizations.