It used to be you could find a box of photos or keepsakes that you inherited to look back on how things were or when you were a kid. Now, most of that is stored on phones, and most parents probably don’t think to share or save them in a way to be passed down in the future.
Survivor bias.
You (generally) only know about physical photographs that have been preserved, and know not of those that have perished.
Digital photos have a higher chance of being preserved because the effort required to duplicate them is trivial. They may be inaccessible though.
I’m not sure that is the case. It’s certainly a trivial effort to switch on backups on your phone, but tge problem it that those backups go away at the same time your phone plan lapses. You’re not going to stumble across great aunt Mabel’s photos of family holidays, because her phone plan, and backups were cancelled when she passed away. It’ll be the same with parents too. Unless they’ve taken the time and effort to curate and share them, they’ll be gone with their owner. If you care about preserving those images, you need to have a conversation with people in your family, and arrange storage that will outlast you.