Plus, amino isn't as regulated as Pokecharms. Pokecharms has been a thing since about 2001 and the rules about Legendaries and Megas had to be added around 2016 due to everyone having one and abusing their powers. Plus, the games and anime are glorified wish-fulfillers, but realistically only a small percentage of people can get Megas and Legendaries and it's never given to them freely.