[secondcoming]

Still, it's probably safer than farming

[Ichthypresbyter]

Possibly true now, but not in Roman times- cave-ins are more dangerous than angry draft animals.

[inglor_cz]

Also, suffocation risk. We are much better at detecting O2 levels, presence of unwanted gases such as CO, and supplying O2 artificially. Ancient Romans lacked both the knowledge and the technology, and most dangerous gases are actually invisible.