While the SDK provides you with valuable tools to develop your app, there also are some usecases where you want to checkout Core Lightning instead.
Metrological Application Platform
If you are planning to make an app for the Metrological Application Platform you are required to make use of the SDK. The SDK provides certain flows and lifecycle hooks required by the system.
Planning to make a TV app, but not sure yet if you want to publish it through the Metrological Application Platform? You could go two ways, with or without the SDK. However the SDK does have a lot of features and together with the CLI tool it will provide you the option to make a separate distributable as well as uploading it to Metrological.
Lightning without the SDK can be used for custom implementations and integrations. While we might not actively support your project, does not mean we are not curious. Feel free to let us know what you are using Lightning for!
Depending on your choice you can look at either of these pages: