Why were the concentration camps not military targets?

If you are talking about the German camps, then it's because the Allies were not exactly aware of the camps, and the Germans routinely transferred the prisoners around to hide them.

The Allies had to get far enough inland to find them, which means they would have to be either flying over without being shot down by anti-aircraft, or they would have to somehow make it past the traps and guards to find them.

Either way, they would need to make it past the Germans to actually find them and know of their existence.

If you are talking about the Japanese camps after Pearl Harbor, then it would be because of the guards and barbed wire. Plus, who would want to go through the trouble of breaking into the camps in the first place?

Explanation:

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.

the term is einsatzgruppen