In retail projects I've been involved in the balustrades to internal voids were about 1200mm. Safer, but imagine an adult carrying a child, even at that height the child is entirely above the balustrade. Not good.
One of the craziest low balustrades I've seen is on top of the "Cheese Grater" in London. Over 200 metres above ground and the balustrade looks like its below the centre of gravity of the man on the right. A gust of wind could present a danger as could a moment of unsteadiness on the part of the man. Here the balustrade should be 1500mm.
|Cheese Grater Balustrade|