Is there a god? Any god?

The Ark has invited Christians to a challenge. So far, as at this posting,  none has taken it up. The one Christian who has commented has only questioned his motives.

My challenge on the other hand is to the godless; non believers, atheists, agnostics and whoever else in between. 

My agnostic friends tell me whether a god is or not and what it is or could be is unknowable but live their lives as if there is no god.

My atheist friends tell me no evidence for a god has been provided. They lack a belief in the existence of gods/ deities. 

My igtheist friends say the notion of god is incoherent and hasn’t been properly defined to warrant a debate on whether a god could exist. 

All these people live their lives as if there is no god. 

My question or challenge simply is to be told why all these groups are reluctant to say there is no god? What is a god to do if one or several were to exist?