I mean, so would artificial wormholes, but we have no idea how to make those either.
Speculative, non-existent technology is not the answer to "why haven't we done this yet". The jury's out on whether or not there's any way to circumvent the speed of light, but if there is, we've no earthly idea how.

Wouldn't the Curvature engine as we currently understand it, the Alcubierre Drive require more energy than the output of the known universe?