We already have Mining. Plus the number of tunnels you're proposing would severly weaken the planet as we already have an unhealthy number of cave systems, sewers, and other underground structures (naturally and artificially formed)
As the others have mentioned, we've already got plenty of methods of getting around via teleportation that tunneling won't be as useful as you think. Plus banks and deposit boxes are already close enough. We have porters, magic notepaper, and other services as well.