I should add that prestige is relative - there are a few "general readership" (non-specific with respect to topic) journals that are considered to be the most p

I should add that prestige is relative - there are a few "general readership" (non-specific with respect to topic) journals that are considered to be the most prestigious, but even within each subfield of research there is a general agreement about the prestige ranking of a particular journal. Especially given the recent proliferation of predatory publishing (pay to publish online with no real peer review), just the history of the journal (that it has existed for more than 20 years) marks it as being legitimate. (Especially reviewing proposals or applications from developing countries, publishing in these legitimate journals this can differentiate serious researchers from the rest.) Even if journals are not considered prestigious in the traditional sense (often measured by what is called an impact factor - related to the average number of citations its papers receive), publishing in them still marks membership in a particular community (e.g., certain types of papers or papers addressing a certain topic have historically been published in X; following the succession of your academic forebearers). So there is a lot of incentive not to scrap the current journals and start anew.