I‘m not sure I understand you correctly. Unchangeable media has several upsides:
no virus or person without physical access can corrupt or destroy the data
even if inserted, nothing can change it
physical media can still be copied and backed up by any and all other means
I do accept that without programs to bypass copy protection, commercial movie discs are kind of a problem. Still, I dont see a problem of using burned discs as a long term storage device.