That's very true, if you tend to leave them lying around here and there. However, you can cut this clutter by having a special place for all your product manuals. That way when a product breaks down, you'll be able to quickly find it and the important warranty information or part number you need.
I like to keep mine in a section of my filing cabinet, but you can also use an expandable folder. These work extremely well for product manuals and keep this folder in one common place. Remember to periodically scan your manuals and remove those you no longer need to keep, because the appliance or product is gone.