Apparently… these things are hi-tech (a.k.a. "ugly") From Men's Fitness:
Together, the jersey and shorts are 31% lighter than the typical NBA uniform. Before, layers of twill were sewn together, bogging down the garment. Now added elements, like conference names and player numbers, are bonded on with a heated glue. From a comfort standpoint, the jerseys are tighter fitting and the seams are heat welded, not sewn. That means better mobility and less abrasion for players inside the uniforms.
Yeah… when I think of NBA uniforms… I'm always thinking "why do they make those guys wear those heavy things? Although, this innovation is cool:
League rules state that jerseys must stay tucked in at all times. The gripper elastic waistband keeps the jersey in place, giving players one less thing to worry about "in the heat of battle."