The less than stellar user experience of many of those encryption tools has been a major contributing factor to that. However, those tools have come long way both feature-wise and as for their usability, for instance have a look at the formidable GPGMail / GPGTools for OS X that makes dealing with public key encryption a breeze.
Nevertheless, anything that makes using encryption easier for the average user is a boon. I’ve always had this vague idea of using public key encryption as a cornerstone for a social networking / contact management service. Public key encryption lends itself to this purpose because keys are not only tied to eMail addresses but they also allow you to verify the identity of a contact by using cryptographic signatures.
Hence, I’ve created a little tool called PrettyGoodSync that takes the name of a vCard file (for example one that contains all your contacts from the OS X Address Book) and a directory path as parameters and then searches the MIT public key server (both GPG and GPGTools ask you to upload your public key to this server upon key generation) for each eMail address in that vCard file. If an entry is found PrettyGoodSync will download the public key as an ASCII-armoured file (.asc), which in turn can be imported into your GPG keyring (via command line or by simply double-clicking if you happen to be using GPGTools).
So far, the tool is pretty basic but its a start. I hope you find it as useful as I do.