@timuralp:
True, it's especially critical before tenure. But for professors of any ambition, the career does not end with tenure. They still want to get things done and publish impressive papers, so that they can have better funding, a higher h-index and more awards than the other guy. So, unless they can somehow manage to do everything solo, a professor's academic success is always directly tied to his/her group.
For students, it's not even always about needing a pep-talk per se. An extreme example, which isn't too extreme for the specific area of research and the level of competition:
One professor used to give out faux medals ("purple hearts") to students who would work the day, the night, and the next day. Straight. That was a synthetic organic chemistry lab, so they routinely handled a lot of toxic and flammable/explosive stuff by themselves and around each other. Not a good mix with fatigue and sleep deprivation, if you ask me. I don't know if those students really needed the "medals" and the encouragement, or if they were insane enough to otherwise regularly do that on their own initiative. But, in any case, the prof had a rule: work 36 hours straight -> get a medal.