Rugs are great for rental properties to prevent wear and tear to the carpets which are required to be professionally cleaned before moving out and possibly replaced if they are beyond cleaning. By laying rugs down on high traffic areas such as hallways heavily soiling of the carpets is prevented, especially in areas where people are entering a house from outside and dragging in mud or water based soils. Care should be taken with long-term placement of rugs on top of carpet, as on natural fibers like wool carpets this can result in the carpet underneath the rug having a different shade of color to the rest of the room, even after the rug is removed and the entire room's carpet is thoroughly cleaned.
Another useful purpose is for covering floorboards typically made of wood. Floorboards are very convenient as they are simple to keep clean, but can leave a house feeling very cold during winter, and they don't feel as nice or comfortable for most people to walk on without shoes. Rugs make a natural fit for houses with floorboards as they are available in a wide variety of sizes to fit any room shape. Regardless of their usage, when rugs are placed in areas with foot traffic regular vacuuming and annual or a half-yearly visits from professional rug cleaners is recommended to keep them free from bacteria and germs, as well as to maintain their visual appearance and prevent wear.
The most important key to rug cleaning is matching the right process and chemical combination for the rug's fiber content. As a general rule wool and silk are the most sensitive of the natural fibers and require gentle approaches - aggressive rug cleaning processes such as steam cleaning or use of aggressive brushes will rip out wool and silk threads resulting in the destruction of your precious rug and an insurance claim for the rug cleaner. On the other hand synthetic fibers used in the construction of machine-made rugs such as polypropylene is are at the other end of the spectrum, requiring aggressive scrubbing to get the best cleaning results.
Other fibers such as acrylic, nylon and so on are in the middle and benefit from a balanced cleaning method which isn't too aggressive nor too gentle in scrubbing the rug fibers. You can often find a rug's fiber content stuck to the backing on an information sheet; when on the phone with a professional rug cleaner give them the fiber information and ask how they would go about cleaning it, to ensure they know how to get the best results for your rug.