The cells that detect a salty taste are located at the back of the tongue. Try applying a little salt to various places on the tongue. There should be a place that feels particularly salty.
In this way, salt stimulates the salt-sensing cells on the tongue. This is why we feel salty.
But sugar does not stimulate the salt-sensing cells even if it touches them. Therefore, we do not feel salty when we lick sugar. Instead, sugar stimulates the cells that feel sweetness.