Because melee and fist of havock is suicide against anything but trash mobs. Same thing for bladedancers. At least they can stealth Rez. A striker loses 75% effectiveness because of 1 hit melee attacks past lvl 24 from any mob that poses a challenge. Sure, you can play as one and just shoot stuff and use grenades. You may even get your special off and be able to escape death, but just hanging back and shooting with grenades is more effective. Why bother when a defender can do the same but actually use most of his tree. Striker is amazing in PVP when you can actually kill stuff with you special, shoulder charge, and melee. But in pve, ward of dawn, team buffs, and force barrier are far more effective. If you're using striker in raids, nightfall, weekly, or lvl 28!daily, you're just screwing your teammates cause of stubbornness.