There are several possible reasons why your stainless steel sink always looks dirty, even after cleaning. Some of the common causes are:

Hard water: Hard water contains minerals such as calcium and magnesium that can leave white spots or stains on your sink. These can be difficult to remove with regular soap and water, and may require a special cleaner or a natural remedy such as vinegar or lemon juice.

Scratches: Stainless steel sinks can get scratched from utensils, pots, pans, and other items that come in contact with the surface. Scratches can make the sink look dull and dirty, and can also trap dirt and bacteria in the grooves. To prevent scratches, avoid using abrasive cleaners or tools, and use a rubber mat or a sink grid to protect the bottom of the sink. To remove scratches, you can try buffing them out with a pumice stone, baking soda, or a commercial product designed for stainless steel.

Grease: Grease from cooking oil, butter, or other fatty foods can build up on your sink and make it look greasy and grimy. Grease can also attract dust and dirt particles, which can further dull the shine of your sink. To remove grease, use a dish soap that cuts through grease, or a baking soda paste that can absorb the oil. Rinse well with hot water and dry with a microfiber cloth.

Stains: Stains from coffee, tea, wine, fruit juice, or other acidic liquids can discolor your sink and make it look stained. Stains can also result from exposure to bleach, ammonia, or other harsh chemicals that can damage the finish of your sink. To prevent stains, rinse your sink with clear water after every use, and avoid leaving acidic or corrosive substances on the surface for too long. To remove stains, use a mild acid such as vinegar or lemon juice, or a cream of tartar paste that can restore the color of your sink.

By following these tips, you can keep your stainless steel sink looking clean and shiny.