As a landing page software, we usually have people hosting their main website elsewhere and just using sub domains on our platform. A CNAME approach allows us to address such use case. Also as a cloud based application, we will constantly have to add more geographically distributed servers to scale our application. We are not a typical web hosting company. This is the same approach used by alternative products like Unbounce, Instapage, Leadpages, Landingi etc.