When our boys were training for altar service, they would routinely show up at Mass and ask Father if they should serve. After a bit, Father told them not to ask, but to tell him that they were ready to serve. Since our parish does not have many servers (and no sign-up sheets), and there are 8 Masses from Saturday to Sunday, this works well.
As homeschoolers, or during the summer, the boys sometimes serve at funerals at our parish, or at the parishes of friends. Recently, at a funeral for the father of a family friend, the boys arrived with cassocks and surplices in hand in case they were needed, but were told that there were already servers; this was unusual, but not unheard of. Assuming that there were other servers at the parish who had volunteered, the boys put everything back in the car, came back in, and sat with the congregation. In came the priest and the pall-bearers, and a woman with a plastic name badge holding the holy water and aspergillum for the priest. She proceeded to take on all the tasks usually reserved for the servers. In fact, there were no other altar servers. The boys were a bit stunned.
Is this typical at some parishes these days?