'If a product or service you buy fails to meet a consumer guarantee, you have the right to ask for a repair, replacement or refund under the Australian Consumer Law. The remedy you're entitled to will depend on whether the issue is major or minor'. If the product bought does not meet the expectations as it was advertised or it broke down within a mere few days of purchase then you should get a refund.
Caveat emptor (Let the buyer beware). Unless some form of warranty is stated, or purchased, or if the law of the land states otherwise, a refund is not required.
Sure, some sellers may find it in their best interest to give a refund anyway because of the effect it may have on future sales. One place I worked would even replace parts (clips that came with the product) for free even if the purchaser admitted to loosing them.
Problem is, not all sellers are selling new products. For instance, if you buy something on ebay or a reconditioned product. There are also small companies that can't afford the loss. After all, you only have the customers word that they use the product as it was intended. Many smaller companies offer to sell a warranty with the product.
Sure, some places like Australia have regulations about it but not every country does.