Store returns are not an ethical issue, but a result of market forces. The more lenient a store is with its return policy, the happier its customers will be, and the more money they'll be inclined to spend there.
For example, managers often have the discretion to extend the duration of stated policies; in my experience, they're happy to do so if it'll please the customer. This costs the stores some money, but the people in charge keep the policies in place, so they must have judged them a net win to their business. I'm happy to take advantage of the convenience it offers me; in fact, I'm more likely to shop at a store with a lax return policy, and likely to buy more, as I know I can return it later if I don't like it. Presumably, it's this tradeoff that the store owners are after.
I understand why it makes good business sense for a company to offer a good return policy, but that is different from me as a consumer buying things on impulse and then returning them a few days later when I regret my decisions.
For example, managers often have the discretion to extend the duration of stated policies; in my experience, they're happy to do so if it'll please the customer. This costs the stores some money, but the people in charge keep the policies in place, so they must have judged them a net win to their business. I'm happy to take advantage of the convenience it offers me; in fact, I'm more likely to shop at a store with a lax return policy, and likely to buy more, as I know I can return it later if I don't like it. Presumably, it's this tradeoff that the store owners are after.