Why are Ice and Water so different elementally speaking when regular ice is just frozen water?

Put it this way: Calling it the ice-type is admittedly a bit of a misnomer. While, yes, most of its associated moves use literal ice, the element’s core actually centers around cold. As such, most of the other elements are reacting to ice’s need or use of cold temperatures, rather than its need or use of frozen water. The only exception to this is the fighting-type, which doubles in strength against ice-types because it’s reacting to the physical fragility of ice against a good whack.