Mmm... using Steem as an example might not fit that strict description...

What I mean: a person doesn’t NEED Steem to access and participate in it - they only need tokens if they desire to hold larger voting power.

Thus, the usefulness and price may be separate issues. A lot of people here have still found Steem useful while price has been low. And given that, price may be related more strictly to speculation and/or the demand for voting influence...