I don't think they're the worst proposals in the world though I share Krugman's general lack of enthusiasm, but I think the simple answer is that Obama's people recognize that while EITC is a good program it also is a program... for poor people. The key thing for adding new programs is to broaden the perception that it's helping ME and PEOPLE LIKE ME, and that involves expanding the scope. Perception doesn't necessarily equal reality, of course, as, for example, Republicans are quite good at convincing people that raising taxes on the top 2% will raise their taxes.
Having said that, in an ideal world we'd have a kind of complete overhaul of all of this stuff in a way which creates progressive taxation+EITC benefits for working poor in a way which does have a very broad base of beneficiaries. And next year hopefully that happens. But I can understand why in an election year it's easier to sell little bits combined with general suggestions of a larger overhaul.
