Whilst yes, as people say, you can just give them money. And the OP might well have done, I've not read them saying either way (admittedly, I've not read all of the posts)

But adding an extra incentive will encourage more people to give money. It's the principle Humble Bundle works by and it has been very successful in getting people who don't normally give charitably an incentive to give charitably.

It might be a sad sociological statement that people getting something out of donating is a bigger incentive than donating out of good will and there will be a lot of people who do give out of good will without expecting something in return. And not all justification is as bleak as "I only care if there's something in it for me", there's a lot of charitable causes in need of attention and people may well have their own rules or principles for giving or be giving to other causes already.

So I don't think it's a crazy idea.