Hello there!
In academia and good writing, we have been taught that texts and speeches must have a good structure according to our purpose, and communicative situation. If your speech has a beginning (intro), a middle (body), and an end (conclusion), you will lay the foundations for a successful speech that fulfills all of your aspirations.
Each part or structure of a text has its own objetive and function; therefore, it's sometimes impossible to change the order without affecting the cohesion and coherence of the text. For example, you cannot go through the middle of your speech (body), part in which usually we develop our main ideas, without having given a contextualization, that is a beginning (intro).
Overall, the structure of a speech is important because it allows us to have an organized, clear, and logic text, qualities that will let us to achieve a good and excellent interchange of idean. In addition, and as an important fact, it will be easier for you to accomplish your goal and the objetive of your speech.
Hope this helps!
If yes, please, mark brainliest :)
Have a good day.