why does the psu need to be on while grounding yourself

[Unknown6]

I am doing an assignment on internal hardware components and I cant find an answer to this question!
How do you ground yourself and why does the P.S.U need to be on while grounding yourself?

 

[americanbrian]

The ground cable is connected to ground through the PSU. If the PSU isn't present then you are not actually connecting to a ground.

 

[wolverine96]

Here's a tutorial I wrote:

How To Ground Yourself When Building Your Computer