The whole point of conferences is to be a paid vacation junket, no? Sure, there's usually some training and networking and marketting of products tied in. But there's a reason they are often hosted in Las Vegas or Orlando.
Vegas is probably the only place that has the capacity to host 30,000+ attendees of the big conferences, e.g. AWS Re:Invent
Huh? Houston hosts multiple conferences that size every year (the Offshore Technology Conference and International Quilt Fair are just two I can think of off the top of my head). Orlando, Dallas, and Denver can all do it as well (though I am not familiar with specific examples there).
But does it still make sense to have conferences so big? re:invent is so big it is extremely hard to actually attend sessions and there are logistics problems like sessions being in different far away locations. Small conferences seems usually more useful to actually connect with people that those kind of massive events.
It makes sense for the companies involved. If someone is attending primarily just to go to sessions, then no. (Although if you're just going for the sessions, I'm not sure most conferences really make sense.)