It is a recent trend after COVID.
Before COVID, having virtual participants or presentations, even live streams were a luxury item.

There was one client I worked with that was an early adopter of zoom pre-pandemic, and they did a lot of multi-venue stuff with presentations happening in all venues, calling out to remote office boardrooms for presentations from that region, stuff like that.
It was charged at a premium (because it was unknown tech, so needed a lot of supplimentary technicians and equipment to mitigate the unknown risks, as well as get the virtual aspects to the same level of production as the in-person aspects).
I’m sure the client saved more on flights and hotels than the extra cost of the virtual aspects of the events. But it was a premium item that not everyone could afford, or was internally set up for.

Post pandemic, live streaming is expected, it’s pretty much a standard option tbh. Every company has their own internal platform (even if it’s just Facebook pro or whatever it’s called) and all event companies have a multi purpose platform if the client wants something different.
Virtual participants are done with a single laptop and no backups (unless it’s a very high level event), expectations from virtual interactions are lower (before, there would have to be analysis of any dropped frames, bitrate drops, stutters etc), and 50-75% of the conferences I do now have virtual presenters.
It’s certainly a lot cheaper, as the tech is now known, it’s capabilities proven during lockdown, and the systems and skills to use it were developed as a standard skillset of techs.

No, I haven’t used any 3d virtual things.
The fanciest I did was a zoom-room to audience wall, but it all got composited into a standard stream.