Why are journal articles kept under an economic lock?

Just a quick moan.  Why are academic journal articles so incredibly expensive to gain access to on-line? It actively discourages informed debates, keeping the knowledge within academia (most universities will have “an institutional log in”).  This means, that in reality no one outside of academia will ever read a journal (unless you’re an expert in one field and have a subscription).

Academics, if you are really studying and researching for the love of your subject, make all your work publicly available! There is little prestige in only having a handful of people read your work. Or make your work available in journals that are open sourced!