These logs could form the basis of a legal record generated by the executive branch of the government and even if they weren't they are likely subject to a legal hold as a result of on-going legal action.
Records in the government sense are very important to form an open trail of policy decisions and overall function of government. Deleting them accidentally can get you a firm slap on the wrist while deleting them intentionally can put you in legal trouble (and worse if you're doing it to cover-up wrongdoing).
The National Archives (NARA) holds on to all the various records generated by the functioning of the federal government for various time periods based on the content of the records. As to payment - costs are incurred in part by the generating agencies and then the taxpayers funding NARA.
Further reading: Privacy Act of 1974, [1], FCC's Comment Filing System System of Records in the Federal Register [2], Paperwork Reduction Act of 1980 (more towards only collecting necessary info), and FCC's Website Notices [3].
[1]: https://www.archives.gov/about
[2, Word .doc]: https://www.fcc.gov/omd/privacyact/documents/records/FCC-CGB...
I have since I actually submitted a comment on this very rulemaking. Your description is correct.
Even in countries implementing the gdpr, I’d expect that metadata is retained in this sort of usecase.