For example, I can easily see someone who, on realizing that his past charitable giving was all about sending signals to his social circle, decides just to stop doing it and spend the money on, say, self-learning resources.

Yes this about sounds like me and most people I know, except that we were not giving at all to begin with, but if we did, it would have been signalling.

I don't 100% understand the usual emotional reasons beyond charitable giving. I do get that in the US or parts of it, social pressure and status plays a role.

But probably a more scalable basis is feeling you have a surplus. To scale it up and out, to different cultures etc. you need to convince people they have a surplus they don't need.

One thing that would really help there is if it was really true.

Alternatively, low unit of measure charities. I.e. those who can do something useful with a unit as little as 5-10 dollars/euros. So that contributors feel they did not just add to the sum that makes something happen but they personally did a person something good.