Why is there is no space where can I dance with strangers in public for free without prior preperation or an exceptional value proposition to prospective partners (e.g. I'll pay you to dance with me, or you get to look at my handsome self - hint: I'm not super handsome). Or is there, and I'm not aware of it? In a foreign country, perhaps?

There are certainly events in Berlin that fit more or less into that category. However often the people who organize an event want to make money with it. Renting rooms costs money.

Dancing with strangers who can't dance (i.e. haven't send time in prior preparation to aquire dancing skills) isn't optimal. In general if you want to dance with strangers it makes a lot of sense to learn dancing.