Conferences are inadvertently excluding many attendees from foreign countries
There is another side to this. Whenever I have organized conferences, I end up receiving lots of requests for invitation letters, typically from researchers in India, for Visa purposes. I absolutely understand this, and I have always done my best to accommodate these requests. But this is time-consuming, and it is very annoying when those researchers (who are sometimes also scheduled to speak) never show up, and never bother giving advance notification.I have since been told that this is a scheme that some people use just to get a VISA for Europe, and then use the time for vacation once they have all paperwork in order.  This creates a bias against researchers from these countries (I have been told by colleagues not to accept requests to speak at conferences from researchers in India because they will "never show up"). Annoyingly, my own experience does somewhat confirm this "advice", and it is extremely unfair for the people that genuinely are interested in traveling to attend conferences.