Why Apple does not revel it’s battery mah

This is a user-to-user forum. No one here can answer a question that begins with “why”. You can find the battery capacity with a web search; many teardown sites have that information. But it’s also irrelevant; what users need to know is how long the battery will last between charges. Knowing the battery capacity alone is useless for that purpose, unless you also know what iOS and every app users in terms of energy.