Because the second Warden changes, the bot stops.
actually as far as i know, tripwire has not gone off since its been implemented. and im pretty sure we haven't had to change anything in order to specifically avoid a warden patch. im not on the core dev team, but as far as i know this is the case.It'd be a never ending battle:
Warden scans for something
HB avoids it
Blizzard reverse engineers HB/DB and scans for it
Tripwire goes off, HB team changes the offsets
Rinse and repeat until the end of time.
Correct me if I'm wrong though.