I agree with your point that there is no use for a currency to make trading between dollars and Euros easier, because almost everyone exchanges Steem to Bitcoin, Bitcoin Cash if he/she is smart IOTA or to the at the moment because of this cryptokiddies-madness blocked/handicapped Ethereum.
So there is no reason to keep so mandy different categories.
But I disagree that it should be the Steem Dollar that should be omitted, because although the value is higher than the dollar many people trust this "term" that it has value because the are used/conditioned to it... This term definitely makes it easier to start steeming...
I even got a new idea while writing this: Instead of real silver, diamonds or platin the Steem(it) society/admins could also collect some Bitcoins and keep it the savings connected to the Bitcoin. So let's eradicate the savings column and make "Save as Bitcoin" -category...
But we almost have to keep the dollar to attract newbies to cryptocurrencies.
I also read many at steemit before I bought some Bitcoins because i wanted to understand this "crypto-trend"...