How would we have known to ask? You'd think the Servants of Light, had they been truly interested in helping us, would have probably given us an indication that the Temples were capable of more if in fact they were.
Perhaps such things had to be freely offered, without prompting, in order to be effective? It does seem logical that if the light were after blood and life force that perhaps an enterprising noble seeking others to bear the burden may have looked to those he traditionally exploited for the solution.
