When reservists receive military pay

Would keeping reserve personnel mean paying people to do nothing?

No. Reservists normally hold civilian jobs and receive military pay when they train or are mobilized.

Reservists normally have civilian jobs between periods of military service. They receive service pay when training or mobilized. Maintaining a reserve therefore does not mean continuously paying everyone to remain idle. Some British MPs also serve as reservists, although explaining how the system works to colleagues can still be difficult.