Why YSK: If you have digital data that is important, (family photos, crypto keys/wallets…). Back it up and prevent permanently losing it.
3 different places its saved to, (iPhone, ICloud, laptop, Facebook, Google, Camera SD, Flash drive…).
2 different media, I would consider iPhone and iCloud the same. Buying two External Drives of the same type and brand too. Why? Consider losing your Apple account or the drive model fails in a year.
1 off site copy. If all your copies are in your house, a flood, fire, tornado, hurricane, EMP… would lose every thing.
0 time to waste. (My own personal add). Do it now. Procrastination is dangerous and is the biggest regret for when things go sideways.
It took me a while to accept cloud storage but I use it now. I backed up all of our family photos on Google photos.
It is an insane tool to get the data moved / shared / copied / transfered quickly. The risk is sharing to sources you didn’t want, like the service provider, (look up Rick and Morty work being deleted due to copyright infringement…off the writers account). Also what if your account is stolen / hacked / deleted and Apple / Google / MS… aren’t being cooperative with recovery.