“...And the hobbits (harfoots are hobbits, btw) are all wearing rags and covered in dirt. They are supposed to be English-cultured and mannered, like Tolkien intended.
At least the dwarves sort of look like dwarves. I don’t think the Scottish accents are accurate, though.” [Telepathic Intruder, post 82]
Shire hobbits were well-off and well-mannered, in accordance with the English cultural milieu the author seems to have had in mind. So were the hobbits of Bree.
But in the chapter “At the Sign of the Prancing Pony,” the author was careful to draw a line between the first two groups and all others - who were dismissed as “Outsiders,” though it was conceded there were a great many more of the latter than was generally supposed.
At the point in the timeline within which the Amazon series appears to be set, hobbit ancestors had not yet enjoyed much contact with either Elves or Numenoreans (Dunedain?) - the sources of all “high” civilization in Middle Earth, and taken up to a greater or lesser degree by every other group except those who worshiped the Enemies or who’d been enslaved by them. So one could argue that grubby and uncouth proto-hobbits are not completely out of the realm of possibility.
Peter Jackson achieved great success in his films, in which all dwarves seemed to have Scottish accents. It might perhaps be unsurprising that this new crop of writers would continue in that vein. Scots have long been looked down on in “pure” English culture as secretive, strange, touchy, violent, not quite to be trusted - a people apart.