It makes sense as HTML was a document format. Document: thing you print, in this case on 90s printers. You need a margin! The genius is you get a reasonable re

It makes sense as HTML was a document format. Document: thing you print, in this case on 90s printers. You need a margin! The genius is you get a reasonable reading experience out of the box with default styles. Noone wants their first character kissing the browser window frame.