okay I won't say it's because people don't know what they are. A lot of people have heared of some sort of memory technique that has a visual aspect to it. That's how humans store information. A lot of people don't understand how to use the properly though. It takes a lot of training to use memory palaces effectively.

I have come across polyglots using memory palaces. But I don't "hang out" in the community so I can't say for sure how many. Most just use the go out and speak it method but from my experience there's not point of doing that if you don't have a decent foundation draw from. Plus I like learning things quick. It's what I'm good at. I'm not a savant. Just like making the most of my time and memory palaces are way more efficient than SRS from my experience.

The reason I haven't isn't because I've been unsuccessful in using it for language learning. It's just because I haven't had time and I want to speed up my current learning as I've never been a consistent learner before.