During years you work under Social Security, your wages are posted to your Social Security record, and you receive Social Security earnings credits based on those wages. These credits are used later to determine your eligibility for Social Security retirement benefits or for disability or survivors benefits if you should become disabled or die.
Earning Social Security credits is a concern not only during current employment but also for prospective future employment after separating from the federal government either to continue working or to retire. CSRS-covered employees especially are interested in this issue because they may wish to work for a certain period in order to earn enough Social Security credits to draw benefits from that system.
That concern is not as significant for employees under CSRS-Offset or FERS because they earn Social Security credits during their government careers. It could be a concern for those who have relatively short working careers, however