I was using a public toilet that had one.

Turned out, you also had to lock the door!

Edit: now that I think about it, it said occupied, but a lady still just walked right in...

What do you think we live in, the future?

Porta potty doors swing closed automatically, so they need the indicator. In public bathrooms, the doors stay open, so if it's closed it's occupied.

$

That's why I just leave the door open like any normal person, duh.

A lot do. Just not all of them.

The mega travel center in the South Eastern US, called Buc-ee's, does have these indicators. However the last time my family was there, my wife encountered a Karen who was concerned she couldn't tell which stalls were open and my wife pointed out the red occupied/green unoccupied indicator on the locks and she was like, "No, I don't know, I'll wait for someone to leave."

Some of them do.

In any case, typically, the ones that aren't occupied are always slightly ajar, so there's no need for an "occupied" indicator.

Most countries have the indicators

To make sure you peek through the gap so you can see someone grundle a dense foshoomp while you try to figure if it's occupied.

How hard is it to press on the stall door and if it doesn't open, just move on to the next?