Give society something it wants, but does not yet know how to get.
Start as an act of creativity because you want something to exist. Build it for yourself. Then figure out how to get it to other people. First give it to the rich people, and eventually scale to everybody else.
Entrepreneurship is an act of creating something new from scratch, predicting the society would want it, and then figuring out how to scale and get it to everybody in a profitable, and self-sustaining way.