Years ago I used to go to Las Vegas just as the National Finals Rodeo was about to start and saw this in several of the bathrooms there.
I’ve read about bib overalls being called “Tennessee Tuxedos.”
My wife had an ass gasket literally disappear recently. She was preparing to use a vault toilet and carefully placed said gasket on the seat. It was a blustery day, and a strong gust came up just before she sat. The wind must have blown across the top of the vent chimney just right to suck the ass gasket off the seat and down into the vault. She was surprised, to say the least.
Thankfully I’ve never had to use one when there was wind, but mine have a habit of either falling into the toilet or tearing completely in two which then is no improvement upon just using TP. (I personally only use an A.G. or TP when I can see just a tiny bit of urine on the lid. Too much and I will use another stall. None at all and whatever the last person did is out of sight, out of mind.)
(But to answer the OPs query, the last time I’ve needed one, the place had it (Disney World.) I don’t know in general because I rarely use them.)
They were common in the restrooms I visited in India when I was there for work.
The men’s rooms at least in VT highway rest stops did not have them. They are the cleanest public rest rooms I have ever seen.
The last time I saw one was on an Amtrak from Boston to NY. And I had to sit because after some modification, the toilet seat would.not.stay.raised on a moving train.