Pain
A successful stencil is incredibly gratifying. I cherish the end result because of the labor I took to get there. There is intense pain in the stenciling process. It grieves me every time I cut a bridge that I wasn't supposed to cut. My fingers burn a raw pink even while cutting out simple designs.
Invasion
So why do stencilers go through with it? The goal of stenciling back when it was first created: near-perfect reproduction in the least time possible. That statement does not make sense any more. What design can't be produced by an artist using digital software? Both traditional artists and new artists are limited by the same thing: their own imagination and skill. All that they dream of they can create. Time-wise, it's fast - lighting fast. In terms of duplication, it's digital! - how much more perfect can one get?
Let me submit to you that unless a new variable is introduced (to the bolded statement above), stenciling would be obsolete. But as we all know, stenciling is alive and well. And that new variable is Setting (place, context, location, etc.).
Why Stencil?
I can understand why guerrilla graffiti artists (vandals) do what they do. Like any form of communication, the goal of stenciling is its message. Guerrillas intend to send a message that otherwise cannot be be sent (due to regulation, financial limits, etc..). For example, one cannot sit and paint on the marble walls of Taj Mahal because it would take too long. It's also illegal. In the same way, one cannot purchase a flashy billboard on the lap of the Abe Lincoln sculpture at Lincoln Memorial, no matter how awesome the design is.
But for the guerrilla, Setting is the new variable that gives his art purpose. It is the fuel that feeds its existence.