There are a number of reasons why you might want to hire a Google AdSense API developer. The most obvious reason is if you want to develop applications that interact with the AdSense API in some way. However, even if you don't plan on developing any applications that use the API, hiring a developer who is familiar with it can still be beneficial. For example, a developer who is familiar with the AdSense API can help you troubleshoot any issues you may have with your existing AdSense account or setup.