but why give him the contract at all? He has shown nothing that indicates he should even be on the roster next year.
Because the decision whether to have him on the roster was made when they drafted him, and not based on 100 minutes of summer league play over the course of 10 days, and rather based on multiple years of college play. He was high on their draft board with a first round grade. They like him. Plain and simple.
James Young and RJ Hunter had 1st round grades as well. I get that Ainge likes him, which is obvious from the contract, but Boston has a real roster problem and I wouldn't have given Demetrius that money given that at least right now.
PG - Thomas, Rozier, Jackson
SG - Bradley, Green, Smart
SF - Crowder, Brown
PF - Johnson, Olynyk, Jerekbo
C - Horford, Zeller
That is 13 people. There are 2 spots left for Hunter, Mickey, Young, Bentil, and Holland. Assuming Hunter and Mickey are in, does Jackson really stand out more than Young, Bentil, and Holland. Maybe he is the guy they go with, but isn't camp the time to really decide that.