> It's never made sense to me why we'd want to kick people out after they've received education here;
That was (probably) never anyone's intention, American representative democracy is just schizophrenic by design. For the same reason the US has never faithfully abided by any treaty, laws and policies rarely end up functioning as intended after the political process.
I don't disagree, although I've also found that I'm often surprised by what people actually think is reasonable policy, and immigration in particular seems to evoke opinions that seem absurd to me but are held by a large enough number of people that I have trouble fathoming.