Comment by jltsiren

Aerial bombardments typically target areas with ~0.01 people/square meter, and those people are often in hardened shelters. A protest may have 1–4 people/square meter out in the open. Attacks targeting the latter cause orders of magnitude more casualties for the same amount of firepower.

And the crowd itself can be deadly if it gets too dense, due to panic or otherwise. For example, there have been at least two crowd collapse events with >1000 deaths in the Mecca pilgrimage.