Sounds easy.
To make local backups I have to do them on schedule, transfer all photos (or rsync them) from all devices to backup media. To have some redundancy I have to make a copy (unless you got a RAID NAS at home that is). In this situation you’ll have a backup as recent as your sync frequency. To access the backups you have to browse the files on the drive, if it’s a NAS, it can be quite convenient, but not if it’s any other kind of storage.
Compare this to for example Google Photos backup. You take a photo, you have Internet connection, it’s synchronized. You don’t worry about redundancy, and can access the photo wherever you are with a very nice app.
Managing digital photos is quite hard to do reliably.
Where do you store them? Optical disc, it might get mushrooms; HDD, mechanism might fail; SSD or flash, this one’s better but it might get corrupted, and so on.
Cloud services provide a convenient solution to all this, than apart from the service going down (which is less likely) have no other issues. You can also access them wherever you are.
Privacy is an important concern. It would be nice to have them encrypted on cloud. Encrypted from a local and trusted (open source) client, that is also convenient. If each time I want to show a photo to my granny I have to download and gpg a file manually, I pass.
But most people don’t care about their privacy at all anyways, so why bother.
Of course it can. Go brute-force a quantum resistant algorithm with a reasonably sized encryption key and call me when you’re done.