you're blind and stupid. there are folds, look closer. on the thigh for example, where the seams intersect. and where the module is installed into the suit on the forearm. plus, the suit covering looks like it's made from a rubber or neoprene-like material in terms of texture, so it makes sense that there are less prominent folds. there is also a type of high elasticity webbing material in the armpits and joints. other factors that affect the look of folds is the lighting. in this instance, it's a soft diffuse lighting.
have you ever tried to bend a beach ball when it's full of air? Space suits aren't inflated, they are pressurized, there is a difference. And unless you are talking about two solid objects connected via a hinge, there will ALWAYS be wrinkles or folds when something bends. Even when you bend a steel bar, the inside curve wrinkles... that's just physics, friend.