Why this SCAR-H Rifle Uses Plastic Ammo Casings

Weapon Analysis

Plastic cased ammunition paired with the SCAR would have been awesome for US soldiers or would it? The SCAR was split into the 5.56mm and the 7.62 x 51mm version. It has had a lot of online hate especially from the Navy Seals. Why is that? The US 75th Ranger Regiment in the Army used it briefly before saying bye to it. Could it have something to do with the insane cost of the rifle compared to the M4.