I'm sure everyone here agrees, the troubles are that:
a) as you correctly
identified, people are people. if they can get a better view, they'll think they're onto a winner
b) sometimes these areas are not just not locked, but also not marked. people have accessed banned places whilst looking for toilets
c) when people find places like this with a better view of the gig, the danger is they invite their friends in too. and some more randoms join them. and before you know it, it's buzzing with people loving the great view. Then you have a real hazard... can the
catwalk take the weight? Can people move around each other without falling?
d) and finally -
regardless of what the public do - if a member of the public can so easily fall off a
catwalk, a member of crew might do it too. just because it's a work area, that does not legitimise things being unsafe.
catwalk handrails and toeboards for crew should meet the same standards you would expect for public walkways, unless other specific fall protection systems are in place