Eeh, more complicated than that. Enforcing age restrictions is an obnoxiously complex issue, even though by all reasonable measures it shouldn't be.

The #1 priority of a con is protecting its panelists & volunteers, and while keeping the panelists comfortable is a critical aspect, enforcement of the conditions they need for adult panels can be a logistical nightmare. It's why so many cons are moving away from having any adult oriented panels at all, and it's really sad to see that the most reasonable solution is to just not have them.