I'm not in a position where EtG would seem reasonable, but I can imagine the psychological obstacles which would arise if I was in that position. E.g.:
If you're one of the x-risk-oriented people (like me), rather than, say, global-poverty-oriented, your money wouldn't typically go to people who are much worse off than you, in Africa and elsewhere. It would typically go to support people like AI and generalist researchers, content creators, event organizers, and their support staff—people who are notably better off than you. They spend their days doing work which feels meaningful and enjoyable, often they live (and pay rent!) in the Bay Area, surrounded by fellow EAs and Rationalists, and they enjoy the high social status that the EA community assigns to people who do direct work.
Meanwhile, you spend 8 hours a day doing… well, a job. The people there might be nice enough, but probably not exactly your kind. You're probably working on something that (roughly speaking) doesn't matter. And your future prospects are gloomy: if you really give away a significant portion of your income, rather than saving up, you'll keep toiling as a wage slave for deeecaaadeees before you can afford to retire.
This is indeed something that might make rational sense (if you're somehow particularly ill-equipped for direct work), but it just feels… unfair?
This post gives an excellent description of some challenges of earning to give:
https://80000hours.org/2015/06/why-i-stopped-earning-to-give/
This post is from 2015, but I think the reasoning is still valid. The author stopped earning to give because he 1) performs better working for a cause he believes is important than for the business he used to work for, 2) does not see excellent giving opportunities and could have more impact by doing something else, 3) had different values than his colleagues.
I sort-of earn to give myself and have similar challenges, but I can overcome them and enjoy being with my colleagues even if their values aren't exactly the same - there are always work-related or everyday life topics we can exchange about. I don't agree that there is a lack of giving opportunities, in 2015 it might have been true. Nowadays more charities and cause areas have been evaluated and there are the EA Funds.
[edited to add a little more nuance]