Time on a cardio machine can be mundane, so many of us will grab a book or magazine to pass the time. I personally can't read while working out, but I know many people can't work out without reading.
If you are a reader, consider putting down your reading materials for a few workouts each week and instead really focus on what your body is doing. After a few sessions, you'll probably find that you're able to get results faster because a focused workout is typically a better workout. One of the best ways to do this but still keep your brain interested is by adding intervals to your cardio session. I have found that it's really hard to focus on anything other than making it to the recovery period during interval training, so it's likely that you won't even miss your tabloid magazine.
Side note: If you simply cannot step on a cardio machine without reading, then by all means, read — I don't want you to get completely discouraged! Just try to find ways to focus your exercise after the cardio is done.