I think a lot of it is what the specific needs of the guests are and their ability to wait in a queue. A lot of people show up to Guest Relations and say they need DAS just because they have a wheelchair. Well nearly all queues are wheelchair accessible now, so they don't need DAS. Or they say they can't stand for long periods, because their knee is bad - well wheelchairs and scooters are an option. So I think they are just trying to crack down on the overall abuse, which is rampant, by having a dedicated team who are more acutely aware of what can and can't be asked. This also helps reduce the wait times at GR, which had become more or less DAS distribution centers.
With the system before DAS, called Guest Assistance Card, they tried to have a series of "specialized" options to combat this fraud. For example, if a guest said they had a condition which prevented them from standing in the sunlight, they'd have a special pass which allowed the guest to have a shaded waiting area. Eventually most GR cast members were just handing out the "unlimited FP" GACs because thats all people would be happy with and it got abused so much that it led to DAS.