They were shipped to Blockbusters for them to place on their shelves so they could have something on their shelves to scan when some one wanted to rent them. They weren't really for promo purposes, but display boxes for renting.
On the us US box "for display only" is written on the bottom left corner. There's no box without this label, because the game wasn't sold separately in the USA, but when Blockbuster sold their stock of games, you could also get the boxes of Mario's Tennis, which were only rent before.