I'm thinking some other swords glow, we just don't know about them!
Elvish magic is the reason...however *that's*
accomplished!
******************
A sudden understanding, a pity mixed with horror, welled up in Bilbo's heart: a glimpse of endless unmarked days without light or hope of betterment, hard stone, cold fish, sneaking and whispering. All these thoughts passed in a flash of a second. He trembled.
The Hobbit, Chapter 5: Riddles in the Dark
Imagination is more important than knowledge.
-Albert Einstein