Here's why:

* Binary ionic compounds are formed from the reaction of a metal and a nonmetal, resulting in a cation (positive ion) and an anion (negative ion). Many common salts fit this description, like NaCl (table salt), KCl, and CaCO3.

* However, there are also salts that are not binary ionic compounds. These include:

* Polyatomic ions: Salts can be formed from the reaction of a metal and a polyatomic ion, like ammonium chloride (NH4Cl) or potassium sulfate (K2SO4).

* Complex salts: These involve coordination complexes with metal ions surrounded by ligands, like [Cu(NH3)4]SO4.

Therefore, while most salts ARE binary ionic compounds, it's not entirely accurate to say ALL salts are.