I've never understood why for many professions age/experience is coveted but engineers are assumed to have such a short shelf life. Nobody prefers a 30 year old lawyer or doctor over a more experienced one but an engineer of the same age needs to start planning a career transition...where is the logic in this?
It could be that the powerful elder members of these groups ensure that their professions don't evolve in a way that would overly favor young people.
For instance, suppose that software engineers were required to hold S.D's (software doctorates, a three year professional doctoral degree that limits enrollment overall to ensure scarcity and severely limit the enrollment of international students). To get this this SJ, you are required to implement things in enterprise java, with massive amounts of complexity, in a way that is difficult to change. Also, scope is broad - making very minor changes to html code is ok for a para-software, but only under the supervision of a licensed member of the Software Bar. Anything involving "programming logic" counts as practicing software, and if you are not a member of the ASA and you do this, you can be imprisoned. In addition, suppose this group used influence over congress to place heavy and database requirements on the business world - in short, forcing them to spend a great deal of money on licensed members of the "American Software Association".
I suspect that under these circumstances, software wouldn't evolve quickly at all.