i started noticing that you can literally shoot people 5 feet infront of you with a rocket launcher and it barely hurts you but you can waste an entire squad of 7 people in 1 shot.
What are you on about?
You understand that the PIAT & Sturmpistole use a similar (shaped charge) system in order to destroy tanks, correct? They have very little explosive filler and are meant to be used against flat surfaces for a reason.
Indeed Sturmpistole and PIAT both anti-tank weapons. Shaped Charge is not a Anti-personel weapon, explosive material is used to turn copper cone in front of charge into molten stream that penetrates targets armor!
yes i understand the PIAT is used for armour but if you take it into a crowded room you can clear it like a old man fart just went off. 
Yes, as the two fellas explained before.
PIAT and Sturmpistole are not your typical Kaboom type of weapons.
Both of them are HEAT shells which fire a concentrated beam of molten copper under a heavy pressure that penetrated the armor. Those shells (especially ones that infantry carry) have a very small damage area since all of the power is concentrated at the front.
Or a quick explanation, they are made specifically to penetrate armor and are only good for that one reason.
yea but still if you take one of those and shoot the ground 5 feet in front of you i can almost certainly guarantee your not gonna just be casually walking away from it