Kevin Sites provides some insight in his latest dispatch about the tunnel system built by the Vietnamese:

They are a marvel of engineering, weaving underground for several stories and linking together living, dining and meeting areas, as well as weapons factories and subterranean hospitals, complete with operating rooms.

But perhaps their most significant function was to allow the VC to coordinate their operations in the south, both by utilizing surprise attacks then disappearing underground, while also inserting agents and saboteurs into the south.

Because of their strategic value, the entrances to the tunnels were well-protected both by camouflage and booby traps.

Yes, the strategic value was a factor but perhaps not as much as the low cost of reducing inhabitant vulnerability with simple countermeasures, which also probably diminished threats as well (few would want to enter an unfamiliar tunnel of traps). Not sure why Kevin ends with these quotes, other than to warn anyone considering a visit to the tunnels to expect a harsh and realistic rather than romantic story:

“We expected it to be about the ingenious ways used to escape detection,” says Nicky Ashby, 26, from London. “But instead, it’s more about techniques of torture with all the booby traps.”

“It seems to me like it’s celebrating the violence rather than the idea of their perseverance,” says another, who doesn’t want to be identified.