Redundancies are often subtle. Very often they simply carry over from our patterns of speech. But part of a writer's job is to be conscious of how he or she is using words and whether clutter is getting in the way of making the message in the text clear. Here's a redundancy at the very end of an article for new mothers that I was editing yesterday evening:
"Most likely, the women in your life have had those same questions, too."
Now on first reading, that doesn't seem so bad, and it sounds almost right. But it is the end of the article, and the writer wants to leave the reader with a strong impression. Now, read the sentence without the "too."