I mean tours where a guide leads people around who have no experience in caving. How do they make sure that there won’t be an unexpected cave-in or shifting, or that an underground river won’t rise? Do they put in reinforcements of any kind?
I don’t have an answer, but I’m curious if this question arose from a recent viewing of The Descent. I just watched it the other night and the same question came to me as they were making their way through.
No, I never watched that. It arose from finding my souvenir from the Ice Mine in Coudersport, PA (which the google search tells me is now defunct 
) and recalling visits to Crystal Caves and Lost River Caverns.
Making a cave ready for commercial tours is probably never a casual event, and certainly doesn’t happen overnight. There will need to be lighting, pathways, handrails, etc. In most cases, some significant rock alterations will be necessary.
All this takes money and time. There’s a high chance that hazards (weak ground, rising water, etc.) will be noticed and dealt with.
Someone has to check for grues. Preferably someone with a lantern and a big sword.
You’re probably much safer in a cave system that has been vetted than you are in something like a slot canyon, which can flood pretty much without warning.
Oh, I have no wish to go spelunking someplace that’s not a tourist attraction. I like looking at the stalactites/gmites, and so forth, but I’ll leave it to the experts to find the safe areas.