Firstly, when they start curating or writing content, they're going to receive some Steem dollars or Steem power. The fact that they're holding that currency, and not giving it away for free, is demand. Holding is demand just as much as buying is demand.
No, just people earning SP and holding it is not demand, at least not in the economics sense as effecting price (which is the context in which you used it). Just people earning steem and not selling it won't increase price. (if they did sell it, it would decrease the price, but if they earn it and just hold it it won't have any effect on price.)
Secondly, the more people join, the more valuable Steem becomes, because Steem can help buy people's attention. Attention is valuable, because it allows you to have influence over people's opinions.
You can't really buy peoples attention with steem. Not unless youre willing to buy a couple million dollars worth. You seriously think someone is going to buy thousands of dollars worth of steem so that their vote can go from a tiny fraction of a cent in value to a slightly larger fraction of a cent in value? thats kind of optimistic
I disagree, and if you'll allow me, I'd like to make the case why holding is indeed demand in the economic sense of affecting price.
If people didn't hold gold, but instead threw it out in the street or in their garbage collection, would it affect the price or not? It would mean that the available supply would increase significantly. The fact that people were willing to throw it out without receiving any money for it, would mean that $0 was an acceptable price for them. If there were other people who did put a non-zero price on gold, any pricing mechanism would have to account for this increase in the supply.
Or to look at it another way, if the largest gold producer in the world decided, instead of selling their gold, that they were going to hold onto all of it, would that affect the price or not?
To put it yet another way, if you bought something and then immediately and extravagantly gave it away for free, flooding the market, how would that affect the price? If you buy, but do not hold, is that really a stable, established demand?
Yet one more way of looking at it, is that, if everyone in the world decided that they didn't want to hold gold, but to sell it, how would that affect the price of gold? Surely if they want to sell it, that must mean a decrease in demand, and an increase in supply, and therefore, the price will go down.
Whether you're buying something or holding something, the effect is the same - a decrease in supply available for purchase. If something is worth enough to you that you take the time to secure it, you are exerting effort to maintain it. So, from one perspective, that means you are constantly "buying" that commodity.
If a couple of million dollars' worth buys a large amount of attention, then ten thousand dollars' worth must buy a small amount of attention. With the amount of Steem power I have, if I look at a post with say 5-10 comments, I can normally decide which comment is going to be at the top. I can also decide which comments will be at the bottom, though normally I abstain from exercising that right. If a company has an advertising budget of millions of dollars, and they understand this technology, do you think it would be worthwhile to invest tens of thousands of dollars in Steem so they can have that kind of influence? Especially considering that, using Steem power, they can upvote their own posts, giving themselves more capital while expending very little energy.
It's not optimistic; it's reality. I can name a few cases of people doing this. For me personally, I could have cashed out some Steem dollars, but instead decided to power up for $1000 or more. @dollarvigilante has done the same, with all of his Steem dollars. @cryptomarket invested 6 BTC in their account when they started.
Perhaps, instead of telling me that people aren't going to do that, you should be asking, why are they already doing that? Of course, it's not purely because they think they can buy people's attention with it, but that's definitely a factor in the equation.
Thanks for your comment and have a good one