It's because their fundamental ethos is pure "enlightened" self-interest, with altruism being viewed as a "sin". They're the quadrant of individualism as the primary ideal, while LibLeft just wants all the government shit out of the way of being "socially" minded.
Freedom has a risk of "Social Darwinism" occurring, or simply put a state of "anarchy" wherein the strong and/or intelligent rule and them being nice and caring is either in their interest or simply because THEIR values so happen to be in-line with being nice
And even then, said nice behavior, maybe selective
Also, the "enlightened self interest" thing feels scary or pressuring in that "Unless you have goods/services and skills worth my time, I won't do transactions that'll help your living standards"