Originally Posted by
IAH-OIL-TRASH
The purpose of the Premier Lines and PreCheck lines is to make it easier/quicker for frequent flyers or premium cabin pax traveling. The inclusion of non-travellers doesn't really help that process.
Gate Pass holders generally don't have any luggage of their own, so they're through the line (especially PreCheck) in seconds. Also, the number of Pass holders is minuscule compared to the number of Premiers in Premier lanes, so the inclusion of non-travelers doesn't hurt that process at all.
So, it's cheaper to put them through the PreCheck line, and it might add a negligible amount of time in the PreCheck line. Why else should they not be allowed PreCheck?