Nobody sent a request to remove them

They turn a blind eye as long as no one files DMCA notice. They do limit downloads of some popular pirated materials behind login though.

The Internet Archive operates under the principle of fair use, which allows the use of copyrighted material for purposes such as criticism, comment, news reporting, teaching, scholarship, or research. They also adhere to legal guidelines and protocols to avoid infringing on copyright laws. Additionally, they often rely on user-contributed content, public domain materials, and works with expired copyrights to build their digital library, which helps mitigate copyright issues. However, they do occasionally face legal challenges or takedown requests, and they respond to those according to the law.