Often return policies will say something like none of these terms should be taken to curtail your statutory rights as a consumer”. What would be different if companies didn’t write these lines?
In one sense, nothing. Absence of such language would not cancel any statutory rights.
One purpose of such language is that the consumer cannot later claim that the company tried to hide those statutory rights. In some consumer protection statutes, attempting to decisive a consumer into thinking that s/he does not have the rights granted by statute may itself be unlawful and a ground for damages.
Also a court may be less likely to void the contract as contrary to the statue, when the contract says that it should be read as subject to the statute and the consumer's rights under it.
Also, once such language becomes common, drafters of corporate contract language often imitate it without thinking what actual purpose it serves.