What's behind this fact that every one can see my posts on Steemit without even being a Steemitian

Well that's the story! In all social networks such as Face Book, Twitter, etc you might get notified about others' updates but you cannot reach the full content unless you log in to your account.

I write a post here on, I share it on my Face Book page. Everyone is happy. They just click the post, they read it and come back to me on Face Book... thank you Farzin. That was great. We wanted to vote you up but we couldn't because we were not members. How great it would be if only members could have access to your contents. At least they may make little effort to join to make use of what they think is useful for them.

Ok, you might want to say: Come on. It is a blogging system. Ok! let it be a blog. Every time I read a post on a blog I can like it or comment on it even without being a blogger. 

Could any body please tell me what's the rationale behind this?