That's an interesting observation.

Also, one wonders why so many big charity donors are anonymous.

Not only asking, but giving is a potentially sensitive act that sometimes (perhaps from modesty) demands discretion/anonymity.

When giving money to a homeless person I notice I'll prefer to do it when nobody is looking, and move on quickly, avoiding too much of a "thank-you".

It's not just that act has to be "Kantian".

There's definitely something about giving that carries the same barrier, and it's remedied by anonymity. I'll put cash money in a charity box, but would never use an identifiable card/digital method.

Charities ought to know this if they're wise. that the "cash-less" society is the death sentence for them.