Thanks for sharing. Probably a bit too cynical for my taste (e.g. you mention many of them are vegan, which may not be the most effective thing you can do, but certainly is evidence for them going out of their way to live in line with their values, yet regarding donating 10% being “unpopular (I wonder why)” you seem to imply they wouldn’t be open to any kind of sacrifice), but I do believe I’ve at least seen a few of these tendencies in others as well as myself, and it makes sense to look out for them.
Also I found your remark on the 10% number rarely being questioned somewhat enlightening, as I myself haven’t done so I’m afraid. Maybe it’s a bit similar to vegetarianism and veganism which are two comparably crowded spots on a continuum of ways to eat. These are easy categories, and once you’re in one of them, it’s easy to communicate it to others and has a clear effect on your self image, i.e. thinking to yourself as “a vegetarian” instead of “<insert random complicated formula of how to evaluate which being you eat and which you don’t”>. Plus it probably works better as a potential role model for others.
With donating 10% (esp. if in combination with the giving what we can pledge) you also end up in such a distinct category. For people who donate less it’s a nice (albeit arguably arbitrary) ideal to look up to. For people who’ve reached it it certainly makes sense to grow beyond it. Although I can imagine people wanting to do good primarily via their career, and donating 10% simply being sort of their baseline, and maybe a way of signalling to the outside world that they’re really living what they preach and as such gaining more credibility. And for signalling purposes, which aren’t inherently bad or anything, it makes sense to settle on a nice round number.