I agree that the older, retrofitted bathrooms are indeed horrible designs. However, I completely disagree that newer bathroom designs are "sane". I have seen very, very few "sane" public bathrooms; usually they're just in fancy restaurants where they don't use the standard metal partitions, and instead spend a lot of money on real walls and tile and wooden doors.

As far as I'm concerned, any public bathroom where the partitions between stalls have any gap at all (especially about 12 inches as they usually are) are not sane. There is no reason for that gap; it's just creepy.

The gap is for easier mopping.

It also lets people check for feet before prying open the door.

It's also for if you have, er, a "wide stance" like former senator Larry Craig.

It also saves 12 inches of material.

It also is an affront to privacy.

They could save lots more material by just not having any partitions at all. Why don't they just do that?

As for checking for feet, airplanes solved that problem decades ago with door latches that indicate "occupied" when they're closed.