Storyfag
Perfidious Pole
Some of the best CRPGs out there do acknowledge the PCs rapid raise to power and do explain it lore-wise. Bloodlines, MotB, KotOR II and hell, even KotOR I.
MotB doesn't. You advance in power because you adventure and gain XP, same as anything in D&D. Bloodlines also doesn't explain it. "Caine has been powering you up" is an unconfirmed theory at best, fan-fiction at worst.
Except you are a devourer of souls in MotB... As for Bloodlines, I'll grant you that it is not explained. But it is acknowledged, multiple times.