I think it's as simple as these guys having the time and money to be available for TV.  How many people can be a "reliable guest" ready to hop on a plane?
odograph -

Indeed, the mainstream media (and I've noticed this particularly on the Lehrer Report0 appears to have a more or less fixed stable of 'experts' on various topics that they draw upon to comment on various news developments as the need arises.

As best I can tell, the main criteria for becoming such a TV expert is i) experience in a high-visibility position in either government or academia, ii) being articulate and reasonably photogenic on TV, and iii) a committment not to say anything too extreme or too divergent from the current 'received wisdom'.

When there is a panel of such people, the atmosphere is generally very chummy, with very little open discord. I recall one rather well-regarded military expert who was on the Lehrer Report during the early days of the Iraq occupation. He said something that went totally against the grain of the other experts and did so quite vehemently. I have not seen him back on the program since.

When looking at this issue, the only thing you need to know is that, first and foremost, TV is entertainment.

In Hindi, a "pandit" is someone who has learned and memorized the Rig Vedas and Upanishads well enough that he can be called upon to recite the right sections for weddings, funerals, et cetera.

Hence the modern expression "pundit." Yergin is the best example of a mass media pundit, but if you'll pardon a ribald touch, it seems to me the book he recites from is the Kama Sutra.

I guess the real question then is : who is getting "screwed"