The main reason most truck manufacturers offer it is because of the high incidence of stolen tailgates. Most of the Big3's trucks have tailgates that can be removed quickly and easily - this made them a hot commodity for amateur thieves.I may be thick but I don't exactly understand the importance of a tailgate lock. Unless one has a hard tonneau cover or cap, isn't it like locking the doors on a convertible? Senseless if you leave the top down, and if a soft top, easy to "get into" with a knife......
OTOH a locking trunk makes sense.
In the case of the Ridgeline, the lock would be primarily used in combination with a tonneau cover.