Does the shares analogy still work?

Greetings you theoretical people you!

As most of you know, the DAC terminology is extremely valuable for understanding blockchains. When you take BitShares from example,
The distributed network = company
BTS = shares of the company
Transaction fees = company's revenue
block rewards = expenses of the company
etc.
This is really helpful in understanding different blockchains and can assist in valuing each ones worth, added value and potential.
What throws me off a bit is that with BitShares, the BTS are the collateral behind the bitUSD. You NEED BTS in order to have a market pegged asset.
With Steem it is a little bit different. You don't need to put up STEEM in order to get a Steem Backed Dollar. You just create both at the same time (well the chain does)
Combined with the fact that there are no transaction fees (the company's revenue in the DAC analogy) makes me wonder where the demand for STEEM resides.
I know that the more STEEM you have the more your votes count when deciding which content gets to the top of the internet. There is definitely value being that.
But at first glance, it appears that STEEM has no revenue sources. What am I missing?
No transaction fees. No sign up fees (the requirement to own STEEM on sign up is not a fee since you keep your STEEM).

What happens when people start cashing out (trading their Steem Backed Dollars for STEEM and getting into Bitcoin or out of crypto entirely)?

Anyone have thoughts on this? Has this already been answered somewhere? If so, link me to it!

Looking forward to see what happens July 4th!

Cheers!