The dealers will readily cut them off for you anytime you ask.
So what good are they?
Determined criminals tend to avoid gun shows.
Idiots that are careless? Not so much.
The cable tie keeps the careless idiot in a safer condition. It does not deter the criminal. The criminal is deterred by the half dozen police officers present, the armed table owners and the ornery clientelle of the show that is heavy on veterans.
I do not see the similarities. There is no heavy police presence in schools, it is a public funded facility, and there is no active handling or trading of firearms or accessories.
The argument against carry at gun shows is similar to the argument against carry at schools because it builds on the "what if" fever and focuses on safety and prevention rather than accountability.
I do know that if loaded guns were expressly allowed for everyone at gun shows, I either wouldn't go, or I would get downright nasty on each and every person that swept me or someone with me with a muzzle. Right now I defensively move myself out of the way and leave it at that. With the REAL potential rather than the traditional rule that the gun is loaded, I'll be banging some safe gun handling into everyone that raises a gun.
And frankly, it's impossible NOT to sweep someone at a gunshow. The tables are all surrounded by people. You either keep it pointed at the ground, or at the ceiling... but it is horizontal on the table. The second it comes off the table it sweeps someone. When the customer is inspecting the gun, he may raise the sights to the far corner of the room and sweep 50 people.
I guess I still come down on "hell, no!" because I don't like being swept, but I know it's unavoidable. Just seen too many ND's to be comfortable with loaded guns in the facility when those guns are in the hands of hobbyists. The table owners and police are OK in my book because they aren't there to shop and swap tall tales... their guns are there to discourage crime/violence/theft.
This argument could be presented to IDPA, IPSC, CASS and the other handgun competitions, BTW. From what I understand (and it's completely possible I'm wrong...), they absolutely do not allow loaded pistols anywhere except on the firing line. You can't load your SAA at a CASS shoot or carry gun at IPSC until you are right on the firing line. When you leave the line you have to unload and clear.