Hey James! Excellent question.
While I did attend a large number of conferences (and gave a talk on some of them myself!) I always had a problem with the fact that some (if not most) of them were freaking expensive.
Not gonna lie, living in Poland that was a part of my motivation to become a tech speaker - a free ticket and opportunity to travel.
I feel like virtual conferences are changing that, I'm glad that there will be more events that are accessible to a much larger audience. (Apart from money, there might be other reasons for not travelling to a conference - for instance needing to take care of family members)
I haven't attended a virtual conference yet myself but I gave a remote talk - it's IMHO a completely different experience. Even though the chat was full I kinda felt alone (because I was, there was no one else in the room).
As usual there are pros and cons and I think that those kind of events will get more popular, I cannot imagine anyone running a 2k+ people conference anytime soon.