In the Royal Navy, the use of impressment to collect sailors resulted in the problem of preventing escape of the unwilling "recruits". The receiving ship was part of the solution; it was difficult to get off the ship without being detected, and in any case most sailors before the mid-19th century did not know how to swim.
Receiving ships were typically older vessels that could still be kept afloat but were no longer seaworthy, or obsolete. The practice was especially common in the age of wooden ships, since the old hulls would remain afloat for many years after they had become too weak to withstand the rigors of the open ocean.