It's the style in Israel now, too. Bennett, Lapid, Hendel, Winter (polo, but close enough), sometimes Golan, all doing the t-shirt thing. All trying to be very warrior-caste and differentiate from the older Netanyahu and the doughier Eisenkot.
Obama on Abdul El-Sayed: "You see those big guns? That's why he wears those t-shirts. I never campaigned in a t-shirt. I ain't got those big guns."