why are all alkalies bases but all bases not alkalies?

Answer 1

An alkali is a soluble base that is dissolved in solution, usually water.
Some bases are not soluble, so they are not alkali's.
Na2O (Sodium Oxide is a soluble base)
CuO (Copper Oxide is an insoluble base)

Na2O when dissolved in water forms the alkali Sodium Hydroxide (NaOH).

So those bases that are not alkali's are the insoluble ones, and those bases that are alkali's are the soluble ones that have been dissolved in a solvent, usually water.