All three are good points but 3rd one is what motivated more people to join Steemit:
They censor people and algo opposing views out of existence
Trolls make it an incredibly negative environment
You don't make money, duh!
...and this is the biggest promotional point as well.
Very good post @joshsigurdson. Bringing Facebook users to Steemit through such posts is a good idea. I myself joined it through one such post by @jerrybanfield.
Steem On!