I use em dashes in my writing to signal a full break—it's a nice way to interject or signal a break between related thoughts, similar to a semicolon or even parentheses.
I use en dashes to illustrate date or number ranges such as 6–7 or March 1–March 31.
I use these punctuation marks because they are the correct marks to use, from the time of moveable type printing.
I want to make some kind of point but I'm tired. Typography is cool, is all.
CSS—which colors and arranges all of the words on the pages of the web—was designed by a human who loved books and typography, and wanted a flexible system for making textual art on the screen. Typesetting, a time-honored human art, brought to the modern age for readers everywhere.