Why does every automation create a new scene?

HomeKit uses scenes to store the actions for automations. An action is like turning on the light, or opening a blind.

If you add an action to an automation, Home+ automatically creates a scenes for you. This scenes has a unique name, which appears as an ID (eg 2DB2F1A1-42A6-49B1-8905-6C3ADC7F6AF4).

But the Apple Home app creates no scene!

Actually the Home app also stores the actions in a scene. But this scenes is protected and does not appear in HomeKit. (FB5777504)

Unfortunately 3rd party apps cannot create this kind of scenes, and therefore have to use a workaround. (FB5987209)