In Game of Thrones, dragonglass seems to be used as weapons against White Walkers.

sam founds arrowhead and other little obsidian object

Jorah fight with dragonglass dagger

Why don't they use dragonglass sword instead of dagger ?

In Game of Thrones, dragonglass seems to be used as weapons against White Walkers.

_{Sam finds an arrow head and other little obsidian object}

_{Jorah fights with dragonglass daggers}

Why don't they use dragonglass swords instead of daggers?