Because we have no choice but to do so: rebuilding it as much as possible identical to how it was is as much writing ourselves into it as novelty is, not that simple stasis has been the consistent rule in past work, anyway.
Whether Church or State or otherwise, communities are evolving entities and the work they produce says something about where they were. Supposing one both can and should mask that is a weird combination of hubris and self-hatred.
That's not to say that restoration as much as practical to the status quo ante is always wrong, but instead that choosing that should be, and be recognized as, as much of an active statement about the present community as choosing novel elements as part of reconstruction is.