Only issue is with not knowing if they were there when the crime was committed.  They can't necessarily charge everyone if say someone was picked up in Muldoon on the way to the gas station. Or if person sitting in back seat is like where are we going and then this person pulls up and robs a guy he's stalking. 

If you're in the back saying dude this isn't right, I don't want anything to do with this and the driver says shut up or I'll shut you up.  You may just sit in the back with your mouth shut praying you get to go home. 

I'm not saying that's what happened.  I'm just explaining why they may not have arrested them on the spot.  Depends on the story given to APD at the time and whether apd feels they can hold/charge them with the amount of info they have on hand. 

It's tough because we don't know all the confines within the rules apd operates with.