No, why is it only in Competetive and only on this map, pls explain that to me?

Well it's only in competitive I am guessing because you are matching with people of similar connection speeds which means if your connection is poor, their connection is going to be poor. In an attempt to minimize your connections problems affecting players with better connections ... And why on that map? Because that is actually one of the more graphically intense crucible maps current in rotation which means rendering is eating up a good bit of your resources not allowing for compensation of your poor networking.