I think this is an incredibly underrated strategy to show you're engagement towards the presenter. It's something that most don't think to do but I believe it's meaningful. In the back of the presenters mind (especially in a virtual scenario), they know that there is always going to be a handful of people that are not engaged. So by showing the speaker that they have your full intention, you are simultaneously improving the quality of their presentation. In turn, that individual will likely become a more confident speaker in the future.