Because. . .
A. They weigh nothing?
B. Dungeons look beautiful by their light?
C. He can?
D. He is a hot guy?
E. All of the above?
Buffy votes for D. Oh, and also B.
Edit: Oh, for Renee, I think the question was that since a torch will eventually burn out if you carry it, does the same apply if left burning on the ground. It seems they will last forever if left burning on the ground.