There are several reasons for this, among them that there were no more targets left in Tokyo itself! COnventional bombing destroyed everything worth hitting.
OF course not. I implied "Japan was nuked" and corrected that with a post right after that.
My point is two Japanese cities were nuked, Tokyo and Dresden were firebombed (and probably killed as many people as the nukes), and these two nations today have no taste for war, one has a Constitution that forbids offensive action, and they are our friends today.
Bringing the horror of war (including massive civilian casualties) has a tendency to make a nation hate war.
Today's soldier fighting soldier, and today's politically correct "don't attack the mosque, even though it is an enemy bunker" style of warfare is a road to continual nonstop warfare.