Facebook Messenger "Suggested List"

Does anyone know how the Facebook Messenger suggested list works?

I just find it really weird - when I go into mine, it shows a list of people that I chat with relatively regularly. Two of my bestfriends, my babysitter, couple of my newer mom friends.

But when my husband goes into his, it shows a list of really random girls. Some are girls he has like never talked with, others are girls he hasnt talked to in years.