Many things that are obvious in retrospect are anything but at the time the important debates happen, and they become obvious in retrospect precisely because someone has come along who paid attention to what - in retrospect - really mattered.

See James Scott's Seeing Like a State (which puts Jacobs' work in that kind of broader perspective, largely in line with calcsam's comment) and Duncan Watt's Everything is Obvious (which lays out the research on why the social sciences are especially prone to that phenomenon).