If you proclaim that CSS is "for vanity", your stables must have an awfully big ladder for getting on your horse.
Shall we take it one step further? Why even bother with HTML, semantic markup is just as much vanity as CSS: just put .txt files on the web. People can trivially copy-and-paste links to other files anyway, they copy-and-paste text all the time. Adding <a> elements is basically just browser candy. As long as the information's high quality, people will want to read it, right?