many reasons already highlighted but in totality:
AB can shoot the 3
he's a GREAT perimeter defender that can guard 2.5 spots
Rozier has proven NOTHING in the nba
danny loves AB
AB is being paid as a starter (relative to the other people on this team)
i'm hoping AB gets 35 mins a night and shines as a showcase to be traded (but i'm not holding my breath on him either shining or being traded)
in a perfect world, Sullinger and AB get moved at some point during this year for a legit Center/rim protector (Alex Len says hello) that enables the 2 guard spot to be freed up for a rotation of Young/Hunter/Rozier/Smart and forces our current "centers" that are just 4s masquerading as 5s, back to their natural spot of playing the 4 next to a legitimate center