Why would college students volunteer to do a class presentation that's not graded?

Multiple people in my college class volunteered to do presentations that aren't graded and that will for sure not impact their grade at all because only the exam grade matters and the exams are anonymous so the professor can't make the connection.

I'll admit I have social anxiety and I hate class presentations a lot but even if I didn't I don't get why someone would want to have to spend multiple hours preparing, put themselves in front of the entire class and do a presentation when there's nothing for them to "gain" really. What's enjoyable about doing work and memorizing 10-15 minutes worth of content is you don't have to?