I don't think that the GPG software is particularly hard to use myself (compared to say configuring Email apps years ago) - but people just "don't want to bother with it" is the *real* problem (especially non-geeks).
I have yet to see that, really. I think a lot of people don't want to learn the "magic" behind it so they can understand what is exactly happening. But as gpg and bitcoin address signing and verifying are becoming more popular for contracts and GPG keys I am pretty sure if you sign it, are legal contracts so yeah, they aren't going anywhere. People better learn or be left in the dust.