same downward pressure on the market as if a content creator or curator did the same
I would tend to agree. Inflation is inflation with much the same effect unless it is actually and effectively directed to pay for activities which add value to Steem. Very little current author and curator rewards fall into this category (it would be nice to try to improve that, but unless we do I think you are right).
why not just eliminate STEEM rewards altogether?
That would be my preference. My proposal on this was to airdrop a STEEMIT (or some other name) SMT onto all STEEM/SP holders and the latter would take over the rewarding function. Everyone can then hold or buy/sell the token or combination of tokens that they desire: the native/core low-inflation bandwidth and governance token (STEEM) or the inflationary rewards token (STEEMIT).
I’m in favor of that proposal.