Audiences are often passive. Typically they defer questions until the end of a one hour scientific presentation. By that time the questions have been forgotten, assuming the speaker has left any time.
Why such passivity? The desire to be polite? Fear of asking a question that reveals ignorance? They'd rather be doing their email?
In any event, passivity is a prescription for getting nothing from a talk. People don't learn effectively in a passive mode, especially when dozens of complicated slides are whizzing by. You as a speaker get nothing if there is no audience reaction. It's lose-lose. You might as well pass out your journal article and let them read that.
The solution? The speaker needs to "break the ice." Tell the audience they can ask questions as they occur, rather than wait until the end. Come with a set of questions that you will toss out to the audience. Give one of your friends advanced warning that you're going to call on him/her if nobody responds. Have another friend set the lower bar by asking a very basic question. Once the "ice is broken," there will be a lot more interaction.