I'm trying to get started with OpenPGP encryption. I understand the concept of keeping your master key safe, and using other keys signed by that key (which can be revoked if stolen) for encryption and other daily use. But I'm confused by the implementation of subkeys specifically. Can't this be done easily without the concept of subkeys? Do subkeys really make it easier? Specifically, the Debian wiki says:
Subkeys are like a separate key pair, but automatically associated with your main key pair.
As far as I can tell, "associated with" here just means that they're automatically grouped together in the UI, for user convenience, but I could achieve the same security by simply creating additional key pairs separately, and signing them with my first key. Is this correct?
The wiki goes on:
The master key pair is quite important.... You should keep your private master key very, very safe. However, keeping all your keys extremely safe is inconvenient...
Subkeys make this easier.... You will use the subkeys for decrypting and signing messages.... You will need to use the master keys only in exceptional circumstances.
So... the purpose of subkeys is to encourage the user to create separate keys for separate purposes, and store and use them separately?
But the UI of GnuPG and several key management GUIs I've used does exactly the opposite of this. It groups keys with their subkeys, assumes by default that you want to copy or move them together, and doesn't always make it clear which key in a set is being used. An entirely separate key would be more suited to this purpose than a subkey, wouldn't it?
Am I missing something? Why are subkeys "automatically associated with your main key pair" - and quite strongly associated, at that - if their purpose is to encourage the user to dissociate them from their main key pair?