Update README.md

README.md

@@ -1,6 +1,13 @@
 # Onyxia API
 
-This is the server part of the Onyxia datalab.  
+This is the server part of the Onyxia datalab.
+
+## Why do we need an API
+
+We could think that Onyxia look like Helm which remove Tiller from its stack.
+In fact an Onyxia user can have no access to kubernetes, this can be important for some installations.
+Onyxia-api give access to the underlying kubernetes cluster.
+
 It interacts with your container orchestrator to deploy users services.  
 Onyxia supports Kubernetes using Helm.  
 Deployable services are listed and configured inside catalogs.  
@@ -110,4 +117,4 @@ This format extension is **fully interoperable** with the official Universe form
 
 The specification is defined [here](docs/specification/README.md).
 
-An example of a Universe using this extension is available [here](https://github.com/inseefrlab/Universe-Datascience).
+An example of a Universe using this extension is available [here](https://github.com/inseefrlab/Universe-Datascience).