On AR-558 they'd been run down and were running out. Any heavy weapons they brought had been damaged or expired.
They're not standard due to the lack of people firing bullets.
Because it's not easily targeted, I don't recall anyone deliberately targeting a bridge? Also there's much more tempting targets and the non-military advantages outweigh the military disadvantages. All the same arguments about why humans have their brains and eyes all up on display rather than burried behind a case of bones!
No idea about the pockets thing. Probably because they're not motivated by the acquisition of things they don't think about places to put their things?