Blu-Ray can degrade, tape fades, hard disks fail, solid state fails, streaming services pull it down.
When my Blu-Ray disc wears down in 100 years of constant watching where am I going to get a replacement? Nothing is forever, just ask HD-DVD, BetaMax, CD-ROM and literally everything else. I've got more bricked USB drives than I know what to do with and a stack of HDDs nearly as tall
How is that even remotely different than it being available on a streaming service? The only media I trust is my Plex server with it's RAID array and even then I'm just barely confident.