The economy turns out to be a pretty big deal, and Commerce Clause aside, states by design have little leverage over it: their borders being open, capital can always just head next door. Small federal government is basically equivalent to right-libertarian economic policy. In an alternate universe you might see liberals content to build welfare states at state level, but in this one it's not really an option.

The framers were well before the Industrial Revolution; if they intended a right-libertarian bias, the economy they wanted unchecked was a smaller and tamer beast than this one. But anyway, they did give us the Commerce Clause.