If the organization carries out a downsizing every time it identifies some unused capacity sitting around, the result is a very heavily loaded remaining work force. Unavailable capacity is required to take on new initiatives as they arise. Protective capacity is required to allow a project to recover from a setback. Projects are, by nature, uncertain. Things go wrong.
Unexpected things happen.
The system may need the reserve provided by having a few extra people on the rolls. The system also needs the reserve that is inherent in the use of overtime and weekends. Working long is only appropriate when the situation truly demands it. So if one sees only wasted cost in unused capacity, the possible reaction of trimming it can do more damage than keeping it around for when it is needed to keep project promises. Part of this pressure stems from the attitude of needing to keep resources busy all the time, which we've already called into question.