There is a very good, detailed explanation of why grounding and earth are so beneficial (although he does not say this directly). This also has to do with why our bodies respond so well to natural environments, like walking on the beach or in nature. If you can find a copy of the movie Grounded, it perfectly explains this simple and life saving practice. Here is an article talking more about it.
Source - 2012: What's the 'real' truth?