I can guess a few reasons: Cost. This may not be cheap. Rebar is often part of a structure’s electrical ground. Any protective current supplied might end up e

I can guess a few reasons: Cost. This may not be cheap. Rebar is often part of a structure’s electrical ground. Any protective current supplied might end up exiting through other connected grounds and doing little good. How do you do this on a bridge? The rebar is one electrode. Where’s the other? Even if you get it working, I would be a bit nervous about the reaction products. If there’s any current flow, then something is being reduced. If the medium is moist concrete, then it might well be water that gets reduced to hydrogen gas and hydroxide ions. The hydroxide ions may be harmless, but the hydrogen could be problematic.