You obviously don't play Brits often, they don't hit as often as Bazookas do because of the nature of there targeting. If a Zooka fires and misses it can still hit - Piat can't.
Tanks suffer a significant accuracy penalty while moving, so playets regularly stop to shoot. The range on the PIATS rival the sniper so as long as you have vision you can often hit them from further away than they can see you. People also underestimate the PIATS a lot. And you can always use attackground to hit them when they are moving. I'm quite good at that.
It's not the easiest weapon to use or the most reliable, but it's still good. I prefer them over bazookas/schrecks since they have such long range and are quite cheap.