For most of history battles where won by moral. To inspire your troops and convince them to fight till victory you are quite literally saving lives as your men will fight harder and the enemy seeing this will be more likely to raut. The faster the battle is over the fewer had to die, before it was over.
Before mickrophones people where more capable of staying quiet when they wanted to hear someone speak, because no one could say instead of me being quiet they should be a mikrophne.
I believe that leaders gave speaches similar to the ones recorded, but the recording fix any gramatical errors repetition and might enbelish some parts tho the speach with a similar purpose and idea was actually spoken.