Because BW had trouble balancing things. There I said the truth (please don't hit me with the mod hammer
I think they chose right - to do a few flashpoints with different mechanics for different factions. For me it's an (the only actually) to want to play both sides.
With different mechanics usually comes different difficulty.
And as someone already said, just because both FP were available at level 10 doesn't mean that the hard mode versions mirror each other.