So their plants and crops can easily have a source of water. And the water is natural and available easily to the people living near the water
Most of the people who live on lakes, rivers, and the sea simply enjoy the water. They usually like some kind of water activity such as fishing, boating, water skiing, wake boarding, swimming, scuba diving, etc.
May because...they want to be close to nature...live in HER cool and beautiful lap...
Maybe because of the scenic view of the beautiful lakes or seas from their houses.