Shoes immediately put you in a certain box, like a style of haircut or a pair of jeans. Even if people can't verbalize it, they can still identify someone as a member of their own tribe.
Curtis is not a fan of product placement unless it's for a reason, but as a costumer you have to use it a certain amount to stay within budget. We needed to use an expensive name brand in that scene, so when it breaks the audience knows how much it costs.