It only creates a lower ceiling in terms of trading arbitrage. Since SBD is pegged underneath to STEEM, the STEEM price would need to go down in order for the amount of SBD to go down. With a pegged SBD, you will still be paid the same amount, but the amount would be worth less in terms of USD given the current prices of SBD.

But having a reliable peg could attract new users as well and increase the price of Steem given that a stable SBD has more use cases and one can earn SBD through Steem-based platforms.

But you make a fair point on the lower potential ceiling. I do not think we get rid of SBD, but should allow transfers from STEEM to SBD that would allow free movement between the two and allow the free market to peg the price.