thank you very much for your answer! I have been a stakeholder for many years (not anymore) but even then I just knew the markets I was involved in.
I didn't know that Twitter and Snapchat were into the red, but it seems to me that it doesn't change the argument about "value": those companies are valuable since their investors and the markets think they will make a profit in the future, and that profit will come just from selling ads and services. So, in the end, the value of these companies is founded on a commercial business, exactly like the value of a newspaper or a television broadcast.
If I am not wrong (but I may be wrong, since I don't know the cryptomarket enough), the cryptocurrencies are valuable for the same reason: the markets and the investors think that they will make a profit in the future, and that profit - as far as I understand - will come from their blockchain technology and the possibility to use it for faster and more safe transactions. Where will the money come from, in that future? I think from the savings and from the competitiveness that faster and cheaper transaction will give. But, as I said, I don't know those markets enough.
As regards on Steem, it has a social community that basically is the engine of the blockchain (as far as I understand!). But, at the moment, the reason for Steem are tradeable for BTC (not directly for fiat!) is just that the market thinks there will be a profitable use of Steem blockchain in the future.
There must be real money, at a point! ;)

(Btw, I have never thought that social media made money from their users, exactly like television broadcasts don't make money from their viewers ;) )