Dicts and sets are supposed to both use {}; {a,b,c} is (conceptually) shorthand for {a:dummy,b:dummy,c:dummy}, where sets (in some cases, including python, opaquely) are actually dicts without the space to store values. (This also shows up in set theory and related mathematics, although there it's dicts that are unusual.)

The rest of your post is a fair point, although I think you underestimate the value of plain ASCII that can be typed on a unassisted keyboard.