> We don't really need multiple exits in case of fire

Tell that to the residents of Grenfell Tower.

Fire escapes are an anachronism for buildings with a smaller footprint that aren't terribly high. Brownstones and smaller (older) apartment buildings in NYC are classic examples. Some of those buildings were also timber framed so having an external and secondary exit was imperative, particularly after major 19th century fire disasters.

What really happened is we started building concrete and steel core buildings that were particularly high so external fire escapes weren't really practical or necessary because the of the building height and the fact that modern buildings typically nearly always have multiple sets of stairs with fire doors, which saved a bunch of lives in one of the WTC towers on 9/11 but not the other (where all 4 staircases were breached).

Having a single point of egress is an incredibly bad idea as evidenced by Grenfell Tower.