We finish big projects and just move straight to the next one, no pause, no marker. There is no in-joke, no habit, nothing that makes us feel like a team instead of a bunch of people at nearby desks. We work side by side and share almost nothing.
More people experience this than they realize.
Your group has no shared rituals to make it feel like a real team.
If this sounds familiar, the Library can help you find the bigger picture.