WTH can't multiple entities be added to an automation action via UI but only YAML

Archive Month of "What the heck?!" (2020)
1

When configuring automations via the UI and you want the automation to trigger a service, the UI has a dropdown to select the related entity the service should be called for. But services support multiple entities and the only way to currently configure multiple entities to be affected is by switching to YAML and add them via

data:
  entity_id:
    - entity.1
    - entity.2

Since there already is logic in lovelace to add multiple entities in f.e. a card, why are we not able to do the same in the automation UI?