Are Cloistered Sisters and Brothers a Waste of People Who Could Be Working For the Church?

Some say that those who pray for the world in cloistered monasteries and convents are a waste because they could be "doing something" like running a hospital or some other ministry such as teaching or working with the poor. I firmly believe one day in Heaven we will all owe a great deal of thanks to the cloistered religious who pray for us night and day.