One of the biggest reasons why you might want to clean your carpet down to the very last fiber would be that you would want it to look clean and perhaps even more importantly you would want to make it smell really amazing too. There is a pretty good chance that your carpet will look perfectly fine once you have gotten it washed by a professional who has a good idea of how things like this tend to work, but suffice it to say that the bad smell that can often come about would be a slightly more difficult thing for you to deal with.
In order to understand why your carpet might smell bad after you have cleaned it, you should learn more about the difference of professional carpet cleaning vs DIY. This is because of the fact that it will help you come to terms with the fact that professional cleaning tends to leave the carpet dryer than DIY methods. The truth of the situation is that even if the fibers of your carpet are dry once the washing procedure has been completed, the backing might still have a bit of moisture in it and failing to dry the backing is one of the most basic rookie mistakes that people might make in this regard.
Making sure that every single inch of your carpet is dry can ensure that no bad smell would ever get in the way of you enjoying it. The fact of the matter is that this is the most common mistakes that you might make, so you would do well to avoid making it lest you start to see mildew forming on your rug.