"BTW, why not instead of burning those SBD, just convert then to STEEM and move to SteemPower of all SteemPower holders?"
Actually I think a better thought vs burning the SBD is to use those SBD to then pay developers to implement items faster and allow Steemit to actually evolve to a powerhouse. There is plenty of work that needs to be done and lots of talent on Steemit to get these items accomplished.
I think burning them and then using something like utopia.io to pay developers makes more sense. That way, we can decrease the supply of steem (increasing the value) and then separately, support the developers by voting for the best contributions. Promotion and development are separate things so I think they shouldn't be connected.
IMO the Supply isn't an issue, exposure is. You can have almost any amount steem out there if enough people want to own it the price will still rise. Using SBD that otherwise would have been burned means zero costs for improvements which can have an exponential effect on the value of Steem vs a minor effect in terms of reduced supply.