Think of a token like owning a taxi medallion in NYC. You can't legally drive a taxi unless you have a medallion, so the price of one fluctuates based on how much money one can earn you and the risk/volatility of those earnings relative to other investment options.
Before Uber, owning a medallion pretty much guaranteed consistent income, so an owner might be happy with a 5% yield for the risk. Uber has changed the market dramatically, so now owners might require a 10% yield because of the added risk.
To be more specific, let's say pre-Uber a medallion owner could expect $50k per year in income. The value of that medallion would be be $1 million ($50k / 5%). Let's say after Uber, an owner can only expect $35k per year, with less certainty. The value would now be $437,500 ($35k / 8%).
Of course, estimating revenue is hard for altcoins because they are so new, but it should get easier in time.
I think the market will transition to this approach in time, but right now altcoins are mostly just trading on pure speculation.
One last point - Similar to tokens, part of what gives a medallion its value is the fact there's a limited supply. Even the risk that more could be added would have an impact on value, which is why understanding hard caps and knowing what happens to unsold tokens is important.
Analogies relating bitcoin to tangible services helps us noobs understand, thanks, this is great!