When introducing steemit to new users, what I tell them is **they can earn for doing the same thing they do on Facebook, YouTube, Instagram and so on**. You see many people show interest. They immediately want to sign up.
I then go on to explain how steemit works for them. How they can be a passive investor and make their steempower work for them or make posts and earn from both author and curation rewards. For me, I think this is the simplest way to explain steemit to a new user and get the person to sign up immediately.