Your roofs are (often) concrete flat roofs with structural floor
The American roofs mentioned are typically significantly inclined, made of a less rigid material (wood, asphalt shingles), and not built to the expectations of supporting as much.
When OP says 'the worst place' they mean it is not a structural place, it is hard to access, and it serves an important function that is best not to mess with.
Note, I do not fully agree with OP but I get the points made.
The American roofs mentioned are typically significantly inclined, made of a less rigid material (wood, asphalt shingles), and not built to the expectations of supporting as much.
When OP says 'the worst place' they mean it is not a structural place, it is hard to access, and it serves an important function that is best not to mess with.
Note, I do not fully agree with OP but I get the points made.