Many tariffs are on components that went into finished goods. In cases like that, consumers may have experienced higher prices but without the importer knowing who they are.
Or goods imported and then sold through a distributor (traditional or marketplace). That final sale was more expensive because the import was more expensive but the distribution channel knows who got the goods, but not how much the increase was and the importer knows the refund amount but not who the customers are.
Because it cost time/money to send money back to their customers