Because the tendency of most new developers is to learn one language and attempt to use it in all cases, even if it is not an optimal application.

I used to see this pattern in VB and later .NET developers, where even when another language or platform would make a task easier or more efficient, they would attempt to hammer out something workable in the one tool they knew, and actively refused (or campaigned) against alternatives.

JavaScript is the new VB.

I love JS =), and no one from my employers know LUA...