Another case of “why we can’t have nice things”. In moderation things work. People start abusing liberties and they have to be taken away cuz people forget how to behave.

Hell, what is the fire-code max occupancy of an Ikea? I know it feels like there are 3000 people in line ahead of you, but I wouldn't be surprised if 3000 was well above the occupancy, not even including the actual customers.

Space wise, 3000 people should be fine for most IKEA stores, they're huge and retail occupancy is about 60 square feet per person [1]. However, ability to egress is probably the limiting factor; there might not be enough emergency exit capacity for that many people.

[1] https://up.codes/s/occupant-load see mercantile in TABLE 1004.1.2 MAXIMUM FLOOR AREA ALLOWANCES PER OCCUPANT, but note warehouse requires 500 square feet per person, which is about half the area of the IKEAs I'm familiar with.