It is training. You are expected to train junior engineers, not just in tech but also in soft skills. Public speaking is a soft skill. It is also something they do in schools. You have to do classroom presentations and reports. I don't think you would make the same argument for them.
Your job should be making you a better employee than you were when you came in (and not just in your hard skills). This is especially true for junior positions. You will be expected to defend your work to your boss and employers. No one is saying to give a talk to an open audience. But you should be able to clearly justify your work.
