I'm guessing it was to show that the team is solid. Teams usually only bring their stars to the show, but maybe DA and co. wanted to show KD that "hey, these are our young guys and were committed to them. The fanbase loves them even if they're not all stars but because they are Celtics. They play hard and give it 100% every night. This is who we are. We're not just a team of mercenaries out for a ring. We're a family and we win together."
Then I'm guessing they were there to back up those claims.