Well, then you apparently believe wrong. The MP7 like the FN P90 was designed as a PDW for second-echelon combat support troops as well as those specialists manning crew-served weapons, communications equipment, and so forth within conventional military forces. In other words, they were designed for soldiers whose primary job is not to fight in the presence of an armed enemy, and who need only defend themselves from lesser rear-area and asymmetric threats. Due to their handy small size, relatively high capacity and ability to penetrate most soft body armour, these PDWs immediately found favour with SOF for low-profile/clandestine operations as well as CQB door-kicking work. But they weren't designed to "slot tangos". They were designed to put down Spetsnaz soldiers wearing archaic Soviet body armour and tin helmets out to 300m from defensive firing positions in the hands of rear-echelon troops. That they were appropriated by SOF for other roles and tasks has nothing to do with their original design intent.