Super-rich liberals favor things like income taxes and inheritance taxes because they keep in place those who want to better themselves while leaving the super-rich liberals largely unaffected.
I don't know exactly how such things work, but I think one of the key notions is that liberals who don't need to much of their money to be liquid can start up "charitable foundations" which do a certain amount of "charity" [favoring the liberals' pet causes of course] while providing the liberals with a nice tax-deductable place to stash their income. When the liberals die, anything they had as personal assets can go into these foundations [tax free of course] which can in turn then earn tax-free investment income until eventually they pay the liberal's heirs (whom the foundations employ). Then, and only then, the liberal's income actually gets taxed for the first time.
Pretty slick system, if you can manage it.