That's kind of silly honestly. I can see where they are coming from but the people at the conference are the good guys. If I were them I would get some of those security professionals to give suggestions on how to have better security. Also random room checks aren't going to catch anything. Anyone who wants to cause harm isn't going have such bad opsec. You will end up catching people with legitimate and highly dangerous stuff like routers, network switches and vacuum cleaners
Just FYI, you need very little skill to clone the WiFi access gateway of a hotel WiFi, and then blast their SSID from your router, to lure close guests into your honeypot. Once people are on your malicious gateway, the fun starts.
In a hotel with hundreds of hackers on alcohol, it's not unlikely for people to fuck around.
There is also no requirement to be a "good guy" to attend the conference.
Defcon is a useful resource for networking and learning. It being run by and for good guys doesn't mean bad guys don't find the event useful. The vague risk of "getting caught" is probably worth taking, regardless of whether that risk is tangible, especially if they follow proper security practices.