I don’t think it’s that they don’t have the incentive. I think it’s because it’s unclear if you give credit to the LLM if that means that OpenAI or similar would be considered an author in which case that could really screw up intellectual property and make using LLMs much less attractive. If the LLM wants attribution then it’s sentient, and if it’s sentient, it may be given personhood (Johnny-five scenario) and get rights, and then it would be a writer, and it could influence the license and intellectual property may belong partially to it unless it willingly became and employee of a ton of companies and organizations or contracted with them.