I don't understand this too much, but my thoughts are like this. If we don't fix this, steem will become bad money, and SBD good money and price of steem will stay on the lower side.
If u get paid in SBD and it's more convenient for you to sell it outside then internally ofc you won't trouble yourself using internal market or convert option.
On the other hand, if the internal market is closer to external ones and there are liquidity rewards with no fee included users might start internal market more.
Although basic user will not bother himself with that much, he will still just take his SBD out and sell them if he wants to cash out his prize.