Probably because usd is strong in most of the regions in asia. For example I am currently in India, here most people earn 300 Rs ( nearly 5 bucks) for full day of labour, and on steemit you can imagine.
I myself referred some people here, and they are liking steemit so far.
It feels good to see smile on their faces when they earn their first buck.
Yes, in a lot of countries earning $5 USD per day is pretty good money. Those are the places Steemit.com will really have an appeal. There are a bunch of new cryptocurrency exchanges being created over there in Asia and that is where a lot of the demand for virtual currencies is coming from. That and some recent law/rule changes only further the demand from that region.