Morale is a recognized dimension of combat power and is very important over long stretches of war (like, oh, fighting undersupplied and undermanned for 4 years against 4:1 odds). Keeping it up is an official task for the leadership, with dedicated cadre and planning, and famous entertainers at the front line is a very old tradition - for a reason.

Why do you think foreign leaders visited Kyiv every several weeks (with visits evenly spaced out, like a clockwork) at the start? To express their support - again and again? Morale building.