The purpose of a permissive license is to encourage proprietary derivatives that come with intellectual property restrictions, EULAs, SaaS with vendor lock-in,

The purpose of a permissive license is to encourage proprietary derivatives that come with intellectual property restrictions, EULAs, SaaS with vendor lock-in, etc. The purpose of a copyleft license is to encourage derivatives that don't come with such restrictions. Copyleft therefore helps reach a local maximum of freedom for everyone as a function of restrictions on redistribution.