Thanks for the reply @kapteinb. You have a very good point! As @jetben2016 states:

here a lot of FB users who can not write a Word document

So FB could be the low-level entry platform that's easy to use by everyone, while Steemit will be more for those who actually post more advanced stuff.

Although if a group of friends join, and they post and upvote each other, then they could post all kinds of stupid shit just to generate money for themselves. I don't know. Let's see how it turns out :)