I struggled with the same thing. However I have come to believe that it is as @dan explains - no matter how unintuitive it is. If you think the other way around, you might intuitively think that everything that has intrinsic value also has some monetary value, which isn't the case. Think air, or time, or happiness. I have come to believe that price/valuation/monetary value and actual value are somewhat totally independent phenomenom.

Another good point is to think about the utility. Who can you pay with bitcoin? Nearly no-one accepts it, so what's the utility? Because of the visible monetary rewards, steem is incredibly attractive to new users who mostly don't care where the value stems from. As a result, there will be lots of people for whom there is very little resistance to accept STEEM or SBD as a tip or payment for something - and so we have a functioning currency with real utility. Where the initial value comes from has very little relevance.

The belief that revenue from transaction costs creates some utility and initial value to the currency turns out to be a circular logic too. Why do you need bitcoin in the first place? To be able to pay transaction fees so you can transact? Transact what? You get it...