More than thousands years cash was the only possible way for charity.

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But nowadays technology very progressed and most of people are using credit cards. This cause the main problem for donations - because even after thousands years they still rely on cash and don't have any other really easy & suitable way, people who want to make a donation simply don't have a method to do it - because they don't have cash, they have credit cards in their pockets. The same problem is for high-volume donations: it's more easy to bring with you a card rather than bunch of notes.