Web Contents have a Translate action that allows translating some fields (text fields and a few more).
We use other types of fields, like documents, images… that usually need also to be translated (for instance, a PDF file can be uploaded in different languages and we need to select each one in the corresponding translation). Thus, we rarely use the Translate interface to translate a web content, because we need to see all fields that need translating.
As the Translate interface is a more efficient way to translate contents, it would be very helpful to be able to translate there all types of fields.