Too vague to be useful

The concept of emphasis has been criticized as overly subjective and vague. It is difficult to say whether an emphasis on the preposed element was really intended or whether the researcher is simply assuming it to exist because of that element’s position at the head of the clause. In addition, the notion of emphasis in and of itself does not explain why and for what purposes the speaker wishes to emphasize something.— Word Order in the Biblical Hebrew Finite Clause, pages 18–19

<idle musing>
In other words, we need a good linguistic reason for the preposing of subjects and/or objects. "Emphasis" is just a catchall term to say "We're not sure, but this seems to make sense." Not terribly convincing, is it?
</idle musing>