Now that systems like ArXiV exist, researchers and taxpayers should not be paying for marketing and typography.
But the real reason journals persist is because readers and promotion/tenure committees want a credibility filter. A really good technological solution to this problem hasn't been found (AFAIK), but I don't see that it would be too hard to build some algorithm to rank articles according to author prestige, institution prestige, number of citations, reader interest, etc. If people want a "hard" metric of article impact, they would be better off using number of citations than journal impact factor anyway.