In the presence of fumes remaining in the apartment is not optimal. Automatic fire doors to isolate would not be possible with a single stair. You would obstruct exit. So if you’re at the non stair end of a level you’re at a survival disadvantage. And the standards need to reflect disabled also.
Developers would love to revert to single stair. The apartments would be slightly cheaper. But is the cost saving worth it?
I also note that sprinkler systems are mandated in the US generally above 75 feet. So these systems would not be currently installed in the 4-6 storey apartment building. It would be an additional cost.
Are you using AI to respond to me? Because what you are saying is not accurate
There may be some jurisdictions where this is the case but it's certainly not the case in the vast majority of the country. I'm curious where you got the 75 foot minimum idea? Whatever source told you that, you should probably discount its likely accuracy going forward.
In single egress buildings, unit entrances are directly onto the stairway — there is no "non-stair end of a level". Egress for a disabled person isn't any different.