It's all odd angles and unusual shapes. A lot of it's pipe. Bad stuff to work on. Once you start to come off it, if you're fallin', there's nothin' to grab. It's not like a beam.
Beams are flat.
Beams have flanges, which are handy for hanging on to, or walking on. They won't let you do that no more. Now, an ironworker on high steel wears a harness that connects him to a safety line. That'd be pretty embarrassing, having to be pulled back up. Then again, better to be embarrassed than dead.