In a previous post, we saw how time consuming it is to calculate with pencil and paper the median salary, or any median of a data set of more than a few data points.
Even after computers became common in the 1950's, and could start doing the work, the mean still was used, because of one further nasty property of medians. Medians require retaining information about every value until the end of the period for which a median is calculated. It you want to know the median salary, you need to save every employee's salary.
Means do not require nearly as much information. In the early days of computers, storing information was expensive, so the mean was still favored for "typical".