Bolts - when you've loosened it enough to get the nut jammed on the damaged threads and don't have time to hacksaw it off. Also cutting the length of a bolt or screwed rod if it's too long - because the bolt cutters cut from both sides they don't bend the steel. They're like a small portable workshop guillotine
Padlocks - on toolboxes(in engineering workshops) when you've lost your key.
Cutting steel rods(dowels), metal straps / fabrication etc.
They're very handy for a multitude of engineering jobs in inaccessable confined spaces too - it was inevitable someone would use them for criminal purposes.
I also used to have a small set of oxy/acetylene gas bottles(gas axe) to take out on site - they would have fitted in a rucksack and what the boltcutters couldn't cut - they could.