Cool [Q] Essentials in updating BusyBox...

Good day!
What is the purpose in updating BusyBox?
And what's with the custom version?

Is it really essential to update this for all user or best only for developers and modifiers?

I asked before I modify this post if the "Auto Update BusyBox" above the BusyBox Pro works without Google Play in my device. I have busybox v1.22.1-stericson installed and found it to be the latest. So I can figure it out on my own soon whenever an update is released. :P