Carpet offers a warmth and softness not found in other surfacing options but it's obviously not for all applications. Carpeting not only comes in a wide variety of colors and patterns but in many different textures as well, making it a versatile style option.
New synthetic fiber technology gives you better alternatives for stain resistance, greater resiliency and even "green" carpeting choices. If natural fibers appeal to you, wool carpeting is still the measure that all synthetic carpets try to emulate, with natural resilience, durability and softness.
Softer surface offers greater cushion and may prevent injury from falls (particularly with infants and elderly)
Easy to replace (more so than wood and tile)
Hides some irregularities in subfloor that wouldn't be possible with a tile floor (without correction)
Stains more readily and spills are harder to clean up as opposed to hard surfaces
Susceptible to damage from water/moisture that can initiate mold growth.
Carpet is considerably less expensive than hardwood materials. While they do need to be replaced every few years, the life of the material can be greatly extended by proper care and maintenance. This makes the long term cost of carpet comparable to certain types of hardwood flooring.