The 3 major reasons, in my opinion are:

1: on Steem you get a secure payment for virtually any content you produce, be it articles, blog posts, videos, photos, drawings, tutorials, songs, compositions, virtually anything that can be read, heard watched, and heck, once the technology allows it, probably even smelled.

2: it's consorship resistant, the blockchain never forgets. People may hide your posts on Steemit with flags, but they're still revisible with a click of a button, also other layouts of the blockchain could display automatically any post, no matter of how controvercial it is. Maybe some even do, I honestly haven't checked eSteem and busy, maybe they have a different approach to this.

3: your profits are decided by the community, not by advertisers, not by corporate overlords, but by simply the balance between the upvotes and the flags you get.