However they're exquisitely busy people, and no one is paying them to spend the time to keep up to date. Sure, there are programs that encourage it (usually called 'Continuing Medical Education') but they're often very weak, easily ignored and there is a lot of pushback by doctors themselves against them). If you take a look at the volume of information coming out every day, coupled with the fact most of the papers just plain suck, you'll realise how it's pretty much impossible to stay afloat.