What you and other people don't understand...
If you create a new damage table for PvP (or just shift it to another stat) then you just create additional testing and balancing issues. Now the developers have to check twice the results every time they make a change. Now its twice as long to roll anything out.
It also creates discrepancies with player expectations. "Hey! This ability usually hits for 2000 in PvE, why the heck does it only hit for 500 in PvP?"
There are many, many reasons to keep the game consistent. Not to mention that PvP gear is often mixed with some PvE gear based on how the player wants to build their stats. This solution, while neat on paper, would be a mess in real life.
What I and others dont get indeed? Im not suggesting a damage table, Its a simple modifier and while errors can occur its not really something that can be broken because its a simple scaling modifier, you could make it more exciting and sexy by adding various clamp values to lock down under/over performance but THAT would be open for mistakes. Its not a wide ranging variation in the theme of what Castle did in City Of Heroes where the game was totally different in PvE and PvP environments, its an elegant way to balance PvP without having to touch on PvE metrics.
As for consistency, pve and pvp mix gear what are you talking about, by the very existence of a expertise stat there is no consistency, and wearing one set of pants does one thing in PvP and something totally different PvE. By very definition of their design PvP and PvE is separate and inconsistant. Its not an approach I agree with but its still there.