The reason it's easy is because you set it up and then you can just forget about it, and then you're doing good things for charity.
I'm more willing to commit to donate $20 to charity 6 months from now, than I am to cough up a $20 this instant.
SwipeGood (and BoA's keep the change program) try to short-circuit this cognitive bias by getting you to commit now, but pay incrementally.