Serving others can mean either working in one occupation to produce money that one then gives away for charitable use or it can mean directly volunteering (and foregoing income) to help those in need.
Somehow, these very noble aims have transformed into being compensated well for spending other people's money.
Look, there's nothing wrong with a career at USAID or whatever gov't agency, but the idea that this career choice is somehow inherently more charitable/generous/service-oriented than any other career choice is frankly ridiculous. However, I've seen many public sector employees make this exact claim, that somehow their profession is more noble, and frankly this has contributed a lot to the current attitudes of those in power and the base who elected them.
But beyond even that, there is actually not a whole lot of merit in doing charity with money that others are forced to give to you under threat of violence. I actually broadly support nationwide charity and would love to see something like what George HW Bush did with his points of light campaign (public campaigns to direct the private contributions of Americans to national causes). But this is a far cry from US AID. There is nothing particularly noble about spending taxpayer money.