haa0014 's Japan Review

The barrel can be removed without damaging it, for example, when a tip breaks off and gets stuck inside.

It is useful if a shaft or tip breaks inside. You could substitute a thumbtack, but no one carries a thumbtack with them all the time.

If you go to play darts often, you should have it.
If you often go out to play darts, you should have it with you. I think it's a good idea to have it with you if you often go out to play darts.