> Were studios really that reckless with their properties?
Some were. Once the film made its money in the theaters it was then put in a vault and forgotten about. The theaters were supposed to return the release prints but sometimes the projectionist would "lose" them. The studio vault those films sat in sometimes catch fire or water leaks in. If the originals are destroyed then hopefully a few release prints are floating around in the hands of theaters, individuals (where those lost prints end up), or television stations. If not, then its gone forever.
It doesn't even take destruction of the property to keep media locked up forever, sometimes even just IP rights. For example original Brave Little Toaster film has never seen an official release in HD because it was produced as a joint venture and nobody has (apparently) been willing or able to hammer out a deal between the various rights holders for a new home video or streaming release.
In 2023 a 4K scan of a theatrical print was uploaded to Youtube and despite the slightly rough state of the print it remains the best quality you can view the film today. There's even a pinned comment under the video from the original director thanking the person who uploaded it to Youtube for preserving their film!
There are several Star Wars film projects that are collecting old film print, negatives, laser disc, etc and using that to remake the original releases. Gemini is very good at listing off all these projects, if you're interested.
Some were. Once the film made its money in the theaters it was then put in a vault and forgotten about. The theaters were supposed to return the release prints but sometimes the projectionist would "lose" them. The studio vault those films sat in sometimes catch fire or water leaks in. If the originals are destroyed then hopefully a few release prints are floating around in the hands of theaters, individuals (where those lost prints end up), or television stations. If not, then its gone forever.