The values are a convention, and that is what makes them useful
Nothing forces a white chip to be worth one. What makes the standard worth following is that everybody already knows it: a player who has been to a cardroom, watched poker on television, or played at somebody else's kitchen table will read your stack correctly without being told. Invent your own scheme and you spend the first twenty minutes of every session explaining it, and somebody still gets it wrong in a big pot.