To make it look good and feel good of course but there’s more to it than that.
The correct cleaning of a rug should extend its life and improve or maintain its appearance. Even if the rug doesn’t get much foot traffic it will still act as a filter capturing airborne pollutants deep within its pile causing potential discolouration and malodour. Foot traffic brings in gritty and oily deposits which combine to wear down the pile. Add a sprinkling of dropped food and drink and perhaps some pet deposits and you’ve a veritable cocktail of soiling!
There is a regularly expressed view that cleaning rugs (or carpets) damages them but this is only likely to be the case if the rug is cleaned incorrectly. For example cleaning residues should be well rinsed out otherwise they will attract soiling and whilst the rug may look good initially it won’t be long before the grubby look re-ppears.