Value is a subjective thing, decided by the consciousness. What your consciousness feels is dictated by chemicals that your brain orders to be sent through your bloodstream. Certain actions, thoughts, sounds, can trigger the release of chemicals that make people feel very good. This motivates them to keep doing something, to release these chemicals again. On the other hand, certain situations can also trigger the release of chemicals that make people feel very bad. This motivates them to do something, to not experience that again.
The prospect of having feel-good chemicals run through your bloodstream. Not everyone can understand this the same way, because there are people where these chemicals aren't as strong, as a consequence they don't get motivated, and have less drive than others.
In a more human-centric way : Certain things feel good, this convinces people to do things that help them achieve that. Not everyone feels things the same way, so some feel less, or not at all.