To understand the value proposition, think about it this way. People pay to advertise on TV because of its reach. You might get your ad out to 50,000 viewers or a big show, maybe 2,000,000 but its expensive and only vaguely targeted.
Many influences have highly specific followers of 50,000+ and you can pick the reach, target market and topic.
For the right brand, done in the right way, it can be highly effective. You reach out to people who are excited about your product, are ready to buy and believe in the person telling them.
Simple, powerful and very valuable.