From what I understand Kloudless is an API proxy to access several competing cloud storage platforms. Most of the time will choose one over another, so why use Kloudless instead of accessing the underlying API directly?
That is a correct understanding, what Kloudless does is provide a uniform interface for 9 different services. So rather than writing the same code slightly differently and/or having to learn 9 different SDKs and dealing with these different interfaces and managing the different tokens (some sources use Oauth1.0a, others OAuth2) you simply tell kloudless which account to access and after your users authenticate you can access it in the same way no matter which storage service they choose.