> We don't really need multiple exits in case of fire because fires are occurring less often and people are getting plenty of warning.

Based on the video, external fire exits were a bad idea from the start and were recommended against 150 years ago, but inertia is hard to overcome.

(unless I Completely misunderstood)

And the problem with interior fire escape stairs was solved by encasing them in concrete and adding self-closing doors to prevent updrafts.

External fire escapes are the best they could do 150 years ago with existing buildings that were a fire trap and clearly better than nothing. However even then they knew they were not ideal.