The reason for Google's action may have to do with the country's crackdown on currency exchange and in Google's letter, the company said that while no specific plans are in the works, it does hope to eventually resume payments to Argentine developers. Meanwhile, Argentine Android users can still buy apps in the Google Play Store and developers can still put up free apps.
Google does suggest one option for Argentine developers who want to continue getting paid for their apps. By moving their account to another country where they can legally do business, Argentine developers can still collect from Google.
source: Celularis (translated), TheVerge via AndroidCentral