Demand and Supply, Desire and Satisfaction

I've been digging my thought about Demand and Supply. Usually it is explained with only numbers. However, I wanted to know what makes it from the underneath.

Desire is in the core of Demand. then Supply should deliver Satisfaction. If not it fails. But there seems to be so many products or services forget it. I see there is a thought pattern issue: when a Supplier sells something, they often just provide stuff they have because that's what they have.. But what missing here is the Supplier might be ignoring the stuff is really demanded or not. And to understand Demand, they need to figure out what Desire is lying underneath.

@bopuc pointed out about identification and measurement of Desire is key. I agree. Demand side seek Supply following their Desire, then we can find markers to identify it.