[inglor_cz]

If you think about the potential risks, it is hard to come up with a different model.

The roof has a maximum capacity, not just physically, but for safe evacuation in case of a sudden problem. Hence the limits on attendance.

You'd like to prevent some idiotic or predatory behavior - no one should be able to throw things down onto the street, take over half of the available space for their influencer recordings or unpack a rope and start an inpromptu tightrope walking performance. Roofs often host telecommunication equipment which is expensive and has some strategic value, you'd like to prevent someone from damaging it or at least have a clear identity of a person that did just that.

It is also a place with very limited escape routes, so any panic may translate into crushed people. E.g. no guns, even empty ones, no explosives, nothing that is easily flammable.