There are a few reasons why this re-targeting makes sense. First, I would bet that multiple stores 'know' you searched for a television, while only one 'knows'

There are a few reasons why this re-targeting makes sense. First, I would bet that multiple stores 'know' you searched for a television, while only one 'knows' you purchased one. The stores that don't know you already made a purchase will keep advertising in the hopes that you choose them, and the one you bought from may not have implemented a feature to 'de-target' you, because their conversion rate is low enough that it doesn't cost them much to keep targeting you. Also, you may return the first one in favor of another, 'better' model; or you may be purchasing for other people or business use.