Think Hiroshima and Nagasaki hadn’t been bombed like tokyo and they wanted pristine targets to show the effect of the bombs, plus the imperial palace was off limits to U.S.A.A.F. bombing.
To kill the person the Japanese revered as a living god might tend to harden their position to the point that even multiple atomic bombings might not get them to surrender.
By all accounts on August 1, 1945, five days before the bombing of Hiroshima, the U.S. Army Air Force dropped one million leaflets over Hiroshima, Nagasaki, and 33 other Japanese cities warning that those cities were going to be destroyed within a few days and advising the residents to leave to save their lives.
One side of the leaflet had a photo of five U.S. bombers unloading bombs and a list of the targeted cities. The other side had the text. The English version of the leaflet is included in an article at the CIA website, “The Information War in the Pacific, 1945,” by Josette H. Williams. OWI stands for Office of War Information:
Front side of OWI notice #2106, dubbed the “LeMay bombing leaflet,” which was delivered to Hiroshima, Nagasaki, and 33 other Japanese cities on 1 August 1945. The Japanese text on the reverse side of the leaflet carried the following warning:
“Read this carefully as it may save your life or the life of a relative or friend. In the next few days, some or all of the cities named on the reverse side will be destroyed by American bombs. These cities contain military installations and workshops or factories which produce military goods. We are determined to destroy all of the tools of the military clique which they are using to prolong this useless war. But, unfortunately, bombs have no eyes. So, in accordance with America’s humanitarian policies, the American Air Force, which does not wish to injure innocent people, now gives you warning to evacuate the cities named and save your lives. America is not fighting the Japanese people but is fighting the military clique which has enslaved the Japanese people. The peace which America will bring will free the people from the oppression of the military clique and mean the emergence of a new and better Japan. You can restore peace by demanding new and good leaders who will end the war. We cannot promise that only these cities will be among those attacked but some or all of them will be, so heed this warning and evacuate these cities immediately.”
https://www.cia.gov/library/center-for-the-study-of-intelligence/kent-csi/docs/v46i3a07p.htm