Here is a copy past quote from the BlockPay slack with the answer :)
that is a big challenge for us, and we are taking it. It will cost us a lot of money to create all the liq for hundred of thousand of dollars floating in. However, it will also boost the price for BTS, and make us more profits, it will also bring more attention to bitshares in general
I worked out a few plans how we can source extra funding for liq creation and to grow the mpa liq. Because think about it . Only with a mpa are you truly free. If we would give you a uia, we hold your money again.. like a bank… we don´t want to do that. we don´t want that your funds can be hacked, stolen, or lost by someone. So we are following our way and give our merchants true financial freedom through mpa´s
Bitshares mpa are a longterm project and will take months and years to grew big into the size of bitcoin, or sometimes it can happen very fast. We just need 2-3 sample projects and other communities will discover the value of mpa´s. We have tons of partners lining up who want to work with us and use a mix of mpa and uia. Most want mpa and are ok to pay down the collateral. That´s awesome :D
Hope that answers your question.
Thanks Chris for the detailed answer :) .
In case anyone else needs it like me :), MPA stands for Market Pegged Assets. @Dantheman wrote a detailed description here: http://bytemaster.github.io/article/2014/12/18/What-are-BitShares-Market-Pegged-Assets/
top thx.