The name of the project is "Let's Encrypt", not "Let's Authenticate the Site Owner".
While I agree completely with the comments about fraudsters, the main purpose of the Let's Encrypt project is to encrypt the communications between the user and the website.
The first sentence on the Let's Encrypt website currently says:
Vital personal and business information flows over the Internet more frequently than ever, and we don't always know when it's happening. It's clear at this point that encrypting is something all of us should be doing....
 
Extensive website owner authentication to eliminate fraudsters is another problem to be solved, separately from encryption. Let's not conflate the two.