The problem is the lack of consistency and obviously, training for the guys who operate the machines.
I've been sent back to check in a baitcaster before because some dickhead was convinced it was a weapon of mass destruction. On the other hand, people I've been travelling with have gotten through with three Stellas or Saltigas with the spools on.
It isn't much of a problem in domestic if you get sent back but in international, that would be a big problem because you've already cleared immigration.