The vast majority of people I know don't know about digital signatures. Most of the remainder can't use them, and are uncertain of how to verify them. The result is that they don't trust them. They all, however, understand and trust a piece of paper with a statement and signature.

Dustin's service doesn't solve that, but your comments are, quite simply, ahead of the game, and detached from current reality. That reality, as is always the way with reality, changing, but that change takes time.

EDIT: First paragraph re-written.