Most managers I know would love to have the ability to prune and rehire staff to rebalance teams and optimise skills, enthusiasm etc. However in many cases (particularly in big companies), managers have very little say in their headcount numbers - most of it being controlled by HR who in turn are watching the bottom line.
As a result, HR can often make it extremely difficult, if not impossible, to hire backfills or additional staff and hence managers quickly learn that it is better to retain a 60% effective person than have no-one at all.
This lesson is even further reinforced when managers are forced to sack staff to hit some corporate cost take-out target which means they have to cut staff regardless of the teams actual resource needs and without the 'low performers' in the team, you would have to cut the good performers.
It's a sad state of affairs, but one I've seen on so many occasions.
Most managers I know would love to have the ability to prune and rehire staff
I bet they would, but such a system would be wide open to abuse. So the market has fixed it: contractors. You can get rid of them easily when no longer needed, but you pay a premium while they are.
As a result, HR can often make it extremely difficult, if not impossible, to hire backfills or additional staff and hence managers quickly learn that it is better to retain a 60% effective person than have no-one at all.
This lesson is even further reinforced when managers are forced to sack staff to hit some corporate cost take-out target which means they have to cut staff regardless of the teams actual resource needs and without the 'low performers' in the team, you would have to cut the good performers.
It's a sad state of affairs, but one I've seen on so many occasions.