To judge from the number of works of fiction I've read where rich characters giving money to charity say the tax write-off is larger than the donation, I think a great many people are unclear on the details of how the tax system works.
I’ve seen that error in just about any discussion of charitable giving, including on HN. I doubt it’s due to a lack of knowledge/skills, because these people would tend to give away all their earnings in the belief to somehow make a profit.