Detergent attracts dirt. This is why its important to rinse out any cleaning solution thoroughly. This is another reason why hot water extraction gets carpet cleaner than the "dry" methods. The bottom line is that you need to rinse well when you clean carpet.
One way to clean stains is with the use of a shop-vac. No, you cant just suck out the stain, but you can repeatedly wash and rinse the area, and suck out the solution each time. This is a more effective method than blotting up the water with cloth, mostly because you wont have the patience to wash, rinse and extract enough times using paper towels or cloth.
