The aim is to influence customers to use your product on their own, again and again without relying on overt calls to action such as ads or promotions.
Nir EyalUsers who continually find value in a product are more likely to tell their friends about it.
Nir EyalIf users are not doing what the designer intended (when users are investing time, effort, etc in your product), the designer may be asking them to do too much.
Nir Eyal