Jim,
ALL of the scholars accept that those ballads Parker, Price, Lanfiere, Wade, Climsall, Deloney, etc., etc., put their names/initials to were theirs. A few from each passed into oral tradition but the majority didn't. Of course we can't prove it, just as we can't prove Harry Clifton wrote his songs. On the other hand nobody has come up with a prior version of any of them, either in ms form or print. The same goes for the broadside ballad writers.

As for RH ballads, apart from about 5, of the other 40 or so they all first appeared in a much printed and reprinted Robin Hood's Garland in the mid 17th century, and I'm quite happy to accept that's where they originated.

As for farmers writing songs, I have plenty of examples of these myself, but they very seldom get the chance to enter oral tradition. In fact none of the ones I recorded were ever sung by anyone else but the writer. There is no reason to believe that your early twentieth century Irish farmer had anything relevant in common with the origins of English songs in any century. I'm well aware Walter sang some political songs but these never had a wide circulation in oral tradition. Of course there are plenty of examples of political songs on the broadsides, but the vast majority came from urban settings and first appeared on the broadsides.

Regarding oral tradition, I'm not aware of having DISMISSED anything.
The origins of something and what happened to it afterwards are two separate issues.

'wrote the ballads and why' In the majority of cases to get their shilling from the printer. (In England that is)