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.
The sad thing is that nowadays this could be easily achieved without any extra cost. Most people have a PC, a smartphone and some soft of cloud storage. Yet people don’t know, or can’t even be bothered until something happens.
E.g. it’s an easy thing to copy your photos to your PC, leave them on the phone, and also sync them to Google photos or something.