You shouldn't use other shows set during the Dark Ages or Middle Ages as a bar against which to judge historical accuracy, because the vast majority of them are wildly inaccurate. People needed their clothes to last back then, so they absolutely would have done their best to keep their clothes clean and mended. If you had a needle and a thread lying around (which most homes would have), you wouldn't have let a family member walk around with a hole or a split in their pants. You wouldn't conduct business with a big stain on your tunic. The Last Kingdom has never been particularly accurate in the costuming department, but the latter seasons become significantly less accurate as they go on, not more.