Hi Richard;
I do agree that there are scenarios that are a little too exposed to be realistic for open cabinets. In the buildings you cite, there may be an apartment manager on site, and in that instance he/she might have a key to a locked enclosure, or be the keeper of the AED itself.
In the latter case, that building would lose much of the educational value of having a visible PAD, but at least it would be there. Hopefully it wouldn't add more than a minute to the response time. The people in such straits must take some responsibility as well - this is not a big money issue.
There are tens of millions of well-heeled people right across America right now, living and working in fancy tower buildings with much less protection than a grouchy old landlady can provide.
So it's not a problem just for the poor, it's an endemic failure to properly deploy a device we all have a right to access in a crisis.