If Amazon etc. was partially responsible for checking the database for you and ensuring listings are properly updated in a reasonable timeframe then it would be more accessible for the average consumer. Even if a consumer doesn't know what UL certification means, if product A has it and product B doesn't and they are similar enough in price, the consumer may opt for product A.

Edit: Reasonable timeframe should probably be dependent on the size/scale/competency of the marketplace platform. In other words, Amazon should be held to a higher standard than a low traffic web store.