Tangential: is it (in)appropriate to use an "admin" theme for a consumer app? Maybe it's semantics, but I see the "feel" of admin pop up on many / most evolved

Tangential: is it (in)appropriate to use an "admin" theme for a consumer app? Maybe it's semantics, but I see the "feel" of admin pop up on many / most evolved consumer applications (e.g. GMail, Kayak, Reddit, Feedly, etc.).