People buy because there is a gap between where they are and where they want to be.
Desires can be anything: Relationships, health, looks, wealth, business, time, productivity, happiness, audience, addiction, social media, organization, taxes, etc.
People have different desires and different levels of intensity for different desires.
Problem is people sell things which people don't desire strongly.
So, to make money on the internet, you have to sell thingss that people desire strongly.