People who enjoy eating enjoy tasting or enjoy the feeling of things going down their throat. Can be psychological too and not attached to the physical stimulus.
Do you guys not like sugar or the sting of spice? The whole ritual around eating, making food or heading somewhere to eat influences how good food makes you feel.
The rivers bring salt to the lakes and ocean that they erode when passing. Those get saltier over time. Evaporation filters that out and feeds the fresh water to everything again, but the salt gets deposited in the more permanent structures.