Why are some apps not allowed in my country?
Regulation and Legal Issues. Regulation and issues with the law are also some other common reason why an app may be available in your friend's country but unsupported in yours. There may be some sort of laws that prohibits or limits the activities of a company or an app in your country.
Why are some apps only available in certain countries?
Many apps are only available in certain countries. Because the laws are different in every country. For instance, some apps use patents from different companies and those companies may have different patents or licensing agreements in various countries.