Why are OSV order languages so rare?

Brian Collins says:

Those are the type of questions only a few people like Bob Dixon are willing to touch with a 17ft pole.

Only Dixon, may his soul be blackened (or indeed blacklisted)? Surely not. Surely we haven’t run out of functionalists in Australia!

Here’s a functionalist take, though it will have some holes in it. I’m not looking up any sources.

• Some languages have strict syntax, and well defined word orders following the template of one of SVO, SOV, etc.
• Some languages have free (or freer) word order, and calling them SVO or SOV is really trying to jam them into a schema by grabbing a default. It’s what typologists have to do, of course, to say anything meaningful.
• Those languages work more according to pragmatic (information-flow) principles of word ordering.
• The pragmatic ordering is typically topic–comment.
• Typically, the topic is the subject, and the predicate is the comment.
• The predicate includes the verb and the object.
• So there is a bias towards SVO and SOV languages, whether they are pragmatically ordered or syntactically ordered: they put the subject first as a topic, and they put the predicate after the subject, as a comment.
• A predicate is a predicate whether the object precedes or follows the verb: what matters is that the object is next to the verb.
• The tendency (again, only a tendency) is towards head–dependent harmony: a language with VO will also tend to put nouns before adjectives, prepositions before nouns, and possessors before possessees. A language with OV will tend to do the opposite.
• It is only a tendency, and in fact English is a notorious counterexample.
• A Verb-fronted language is possible: the bias towards SVO and SOV does not exclude them. In fact, Celtic VSO languages developed out of SOV Indo-European, and Greek SVO gave rise to Cypriot, which has been argued to be VSO.
• I’m vague as to what process fronts verbs historically, but it’s clearly a thing. Brian probably knows more about it, if he’s bringing up prefixing.
• OSV and OVS are extremely rare, and you’d expect that. Whatever process is putting the O first, it’s not a commonplace one, and you’d expect it’s a fluke, rather than whatever commonish process fronts V. OSV in particular breaks up the predicate (O and V), and buries the S mid-sentence (where it isn’t going to be a topic). But OVS, which at least keeps the predicate together, is not substantially more common.