The reason laundry smells of detergent when wet but not once dry is due to the process of evaporation and the way our sense of smell works.
When you wash your laundry with detergent, the detergent molecules become dispersed in the water, and they bind to dirt, oils, and odors present in the fabrics. As a result, the wet laundry will have a noticeable detergent scent because the detergent molecules are still present in the water surrounding the fibers of the fabric.
However, when you dry the laundry, the water evaporates, taking the detergent molecules with it. As the water evaporates, the detergent scent dissipates along with it. Once the laundry is completely dry, there is no water to carry the detergent molecules, so the scent is no longer detectable by our sense of smell.
Additionally, as the laundry dries, it may pick up other scents from the environment or from the dryer sheets used during the drying process, which could potentially mask the detergent scent.
In summary, the detergent scent is most noticeable when the laundry is wet because the detergent molecules are suspended in the water. Once the laundry dries and the water evaporates, the detergent scent dissipates, leaving your laundry with a neutral or freshly cleaned scent.