From a network engineering perspective, it's pretty easy not to decrement the TTL (keeping devices from "appearing" in a traceroute). Hell, this is pretty much

From a network engineering perspective, it's pretty easy not to decrement the TTL (keeping devices from "appearing" in a traceroute). Hell, this is pretty much the norm where MPLS is concerned. Your packet may hop through a dozen routers along its way without showing up in a traceroute -- you just see it go in one side (then it goes through a dozen routers) and you see it come out the other side.