Like CT I have always found it amusing that the economics job market is so much better institutionalized than those in sociology and political science. One possible explanation is just that economists have a better understanding of Coase's theory of the firm and so have a better sense of which activities should be inside institutions and which things should be outside institutions.
An alternative explanation is that, due to their higher value of time (the implication of higher salaries), economists may be less likely to spend time fighting over trivia, which may make organizing a market easier. An interesting study would examine the amount of time faculty in different disciplines spend in department meetings, conditional on department size and the age distribution of faculty. One would expect a negative relationship with average salaries.
A third explanation is that economists do a lot more hiring than sociology and political science, which means that it is easier to justify the fixed costs of both setting up and operating the job market institutions.