I suspect that wormholes represent a spurious solution of the Einstein field equations. When solving differential equations modeling nature it is not uncommon to come up with a spurious solution that mathematically satisfies the original equation. The result merely represents a limitation of the model and has no physical significance (like the imaginary solutions of the Pythagoras equation).

A case in point is the Landau-Squire jet which is a closed form solution of the steady Navier-Stokes equations (it is described in many text books on fluid mechanics). The Landau-Squire jet is a discrete flow described by a self-similar coordinate system (it has no characteristic length). A discrete flow with no characteristic length is self contradictory. The Landau-Squire jet is actually the asymptotic result of an unsteady jet. The starting process introduces a length scale which then gets washed out after an infinite length of time. The modeling assumption of steadiness allows for the mathematical solution but you'd never actually see one in the physcial world.

Gary