Unfortunately, as far as im aware, we generally are skimping. In the videos I linked above, it's explained (with sources!) that most of the "issues" which the Fire Chiefs Association raises are issues in dual stairwell buildings as well. This is because of a number of factors, but includes items such as:

• In the case that a fire breaches the containment of an apartment unit and spreads to the rest of the building, one stairwell is often allowed to burn relatively uncontrolled so that firefighters can focus on evacuating residents instead

• The long hallways of dual stairwell buildings mean that it's more likely for residents to get cut off from a safe stairwell, or need to travel a longer distance to a safe stairwell, vs single stairwell buildings where the stairs are right there

• As dual stairwell buildings often end up with only 1 usable stairwell in the case of a fire, it's a little silly to say that dual stairwell buildings allow residents coming down to not obstruct firefighters going up (especially when you consider that even with 2 stairwells, you can't control which one people will use, even if both are functional)

• Finally, for what it's worth, my understanding is that positive pressure halls/staircases do aide greatly, even in the case that a fire is directly in the hall as they keep smoke from settling.

Edit: forgot two:

• they're in quite a few buildings now, but implementing widespread sprinkler systems in apartments is shown to contain fires to a room 96.2% of the time. (There's a few different figures for this, but it generally seems to be between 88-97% effective)

• IMPLEMENTING WIDESPREAD AND MANDAROTY TESTING OF SAFETY MEASURES. The majority of major & lethal fires are caused by faulty, untested, or otherwise nonexistent fire safety equipment. Requiring proper testing of sprinkler systems, fire alarms, ventilation, validation of building integrity, and other measures could greatly reduce fire danger in north american apartments, regardless of how many staircases they have.