What is another use for themes in a speech

Themes in a speech help to tie a speech together and make it coherent by marshaling all the facts around a central idea to drive home a point like talking about why the US blockade on Cuba should be lifted since it only damages a small peaceful country on the doorstep of the US and whose social system should be respected and which could benefit both countries and foster a friendly relationship and allow for example the advanced Cuban medicine to be benefitted from by Americans.