Apple's biggest income growth is services like iCloud. There is no way they are going to give up that money spigot. Decentralization would mean losing out on that sweet sweet service profit. Especially as other companies undercut them
It easy to see why. When you first open your new iPhone it backs up to iCloud, you get 5GB free and the first backup takes ~4.5GB. Now it will remind you endlessly that your iCloud is nearly full. It's only £0.99 a month to make them shut up...
Not my OOTB experience at all; an iCloud backup of a new, nearly empty phone is vanishingly small.
That said, shoot a bunch of 48Mpx pics + 4K vids and you're going to fill those 5GB quite quickly.
Rven the 200GB package (2.99€?) is only 36€ a year and should last most normal _families_ when shared.