Why was a strong, combat-ready army tender to the Spartans in peacetime?

This can be explained by the fact that there were many more slaves in Sparta than full citizens. The bulk of the slaves were helots, which were 5-6 times more than the Spartans themselves. In this connection, the helots very often rebelled against Sparta, thus, the Spartans always had to have a strong and efficient army at hand, which could pacify the rebellion at any moment.