Any developer could tell you that it's because that would be extra code, extra UI, extra localization, extra QA, etc. for something nonessential that could be ignored in favor of adding something that increases the chance of the game managing to break even.
Any developer could tell you that it's because that would be extra code, extra UI, extra localization, extra QA, etc. for something nonessential that could be ignored in favor of adding something that increases the chance of the game managing to break even.