There are two types of dashes. One is the "n-dash" (or "en-dash"), which takes up one space, and is most often used to hyphenate words; and the other is the "m-dash" (or "em-dash) which takes up two spaces, and is most often used to bracket off parenthetical information within a sentence, like kind of a lighter weight parentheses. Em-dashes get used a lot in novels and other published writing that is subject to correction from a professional copy editor, but very rarely in the daily typing of regular people. So now when people see it getting used they just assume it must be a clanker.