Check out the twist-to-lock sockets in Japan! Super common there, but I've never seen these in the US, even though the plug is basically identical.
NEMA L6-30R is a locking 208/240v 30 amp receptacle. L means locking, the 6 means two hots and a ground at 208v or 240v, (240v for 240v split phase and 208v for 208v 3p wye) 30 is amp max amps, R means receptacle.
Twistlocks are also used a lot in Theater lighting, and movie/tv production.
Also, some generators.
But yes, in general, not so common for residential, and only certain commercial tasks.