Its useful for darksiders or for those who cant use every bit of pixel as a bank. And ofcourse they complicate. You cant say if someone placed girder only for bouncing purposes, bng is about whole map and girder may block some shots.
I dont know if ive seen that, surely didnt pay much attention if that happened (in kaos for example). Torching mine and getting damaged isnt something extremely rare, though nice find there Im suprised.