"all it takes" is a very naive simplification of how to accomplish this solution and is much more complicated for a non tech savvy person than just hitting "yes" on a backup option their phone prompts them for.
I feel like you must be in a social bubble if you think this is a task the average Walmart American views as easy. These devices also are typically marketed for PC backup and don't usually make backing up their phones "easy". It also is something they'd have to regularly remember to do. It's substantially easier for a user to have their photos immediately and automatically backed up to icloud or Google Photos, and you're being intentionally obtuse if you're suggesting otherwise.
It's also not at all appropriate to claim people are "developmentally challenged" simply because they don't feel comfortable backing up their own data regularly to an external device. As such I have also flagged your comment.
