Selected answers from the Dumb SEO Questions Facebook & G+ community.
Chase Reiner: Why does or did (not sure if still required) Google's Search Console ask to add www and non www properties?
Jim Munro: www is a subdomain and the root domain is also subdomain (of the parent domain .com). Also people have valid subdomains like santabarbara.domain.com as well as sub.sub.domain.com etc.
No disclaimers needed, Chase. :)
Kapil Bhardwaj: It's a small part of Google provide better result for your website. Once you tell us your preferred domain name (www and non www) , they use that information for all future crawls of your site and indexing refreshes.
Neeraj Pandey: Also, It helps you see how your page index & backlink profile is running . if you have set www so in ur non www version the index status would be showing how your non www pages are indexing preferably in such case it shouldn't be indexing the same is for backlink
Why does or did (not sure if still required) Google`s Search Console ask to add www and non www properties? 
