If you are going to boost people at 55 in PvP you might as well boost PvE as well.
It is only fair.
It would ruin the thing that built TOR: story. PvP has little story to it, just some background on the warzones. Now imagine a level 14 being bolstered up to face the Battle of Ilum. What? Where is Ilum? There is a war? Who is Malgus? Why am I dying?
The further we are from PVE bolster, the better.