Nancy Fulda has an excellent post about her theory on Why Modern Readers are Less Tolerant of Description, which rings totally true to me.
One hundred years ago, or even fifty years ago, the average reader did not travel widely and did not have access to full-color photographs or television. They had never seen pyramids, or elephants, or tropical rain forests. Many people had also never seen a prairie, a pine forest, a stretch of English farmland, or an industrial city. This means that the reader’s repetoire of pre-conceived images was not as vast as the modern reader’s.
I think much of her post is also true for dialects in fiction. Once upon a time, not only was it possible for someone to have never heard a German accent, but it was also likely that they would be called upon to read that passage aloud. So writing dialects phonetically helped the reader. Fashions and readers’ expectations change.