Why isn't necrophilia legal if given consent?

If a person is to give consent pre-disease to another individual to have sexual intimacy with their body, why is it illegal? Laws only affect property and living people. If the person before death signs a legal document stating someone can, the arguements I've heard is because the person is a corpse and cannot give consent, but if you think about it, how do wills work then? It's consent to give away your property to others, and your body is your property. You can say it's immoral to commit necrophilia, but itn't it just as immoral to take away constitution rights based on other people morals when two or more people agree upon necrophilia? Isn't it also equally immoral to judge others based on their sexual attractions, but taking their rights away from them? Corpses have no rights, and yet wills apply, and necrophilia is a victimless crime. If it affects family members, why isn't pornography illegal if it affects how the person family feels, despite giving consent to the producers to be in the film? I dont really see the big deal. I think it's more wrong in fact to judge people based on sexual attractions, take away their rights, and make exceptions to our rights to fit to the moral code of our general society when none of those people are directly affected by it, in which case everything in life should be illegal since anything could theoretically indirectly affect another person negatively.