1 and 2 will probably make sense to some. It's not something that would overcome my why not.
For 3 the biggest problem with encryption is you introduce a single point of failure, if you lose access to the keys your photos are gone.
On a simpler note I'm a big fan of keeping things as simple as I can. Encryption is not simple. It can be fun to work with and I don't want to ignore that but unless you want to do that for fun I don't think it's worth the complexity.
If you use restic for backups there is not even an option to do it without encryption. Just use something simple you will never forget. Everybody has that password.
I don't encrypt them because then if I lose the encryption key or the encryption program or the encryption program won't run on my future machine, I lose it all.
Perhaps some family photos would include sexy time memories? Ideally those are password protected though or not included with general family photo storage..
It's easy to say "Encrypt everything," but how do you go about it? For folks looking for an "easy" cross-platform solution to encrypt your sensitive bits in the cloud, check out Cryptomator [^1].
Restic. If you create a restic backup it asks you for an encryption password, you enter it, co fogure the folders etc.
Sadly it has no gui (that I know of) but something like runtestic can help with automated incremental and encrypted backups, where you only want to keep the last n versions (and for example a weekly snapshot)