I think this is a bit of a small-scale conway's law-style effect. You shield your ability to reason about the code from the complexity of the code of others by abstracting around it, thus increasing the total complexity with an ad-hoc abstraction layer.

Essentially for every layer of indirection, a reset of complexity happens at the expense of unknown unknown's creeping into the simulacrum the layer is modeled as. At least, that's how I see it. :)