Why? The Hoth is the only blaster that had them.
I thought the consensus was the Bespin blasters had no obvious views of the piston side and it was conceivable that they did in fact have them installed. I ordered three piston sets and all of my ESB blasters will have them. Of course, I build idealized blasters, not screen accurate. Don't forget, it's better to regret something that you have done instead of something you haven't.