When you present in front of a (large) group of people you bring together these persons in one location. You and they may need to travel to this location. There may also be risks at the location itself for accidents to occur.
The more people you bring together to more risks. Who is responsible for the consequences in case an accident occurs? What happens when you or some members of your audience can’t reach the location? Who is responsible for what and what is the maximum exposure? For various risks you can get a level of insurance to mitigate your exposure. Think about the insurance that is needed in relation to a presentation for a group of people. Are you covered?