We have a limited number of licenses for this software and we have various people in the company who may need to use the software once a year for a few days to a few weeks or may not ever need it.
So now we go around installing and removing software on workstations as needed so we don't have more copies installed than we are licensed for
Sometimes we run out of licenses and we don't know if some of the people assigned software may no longer need it and can give up their license while others who need it are being denied access.
We cannot just buy a copy of the software for every employee who might possibly ever need it one day in the future and keep it permenantly on their PC because that would be astronomically expensive (I was told several thousand dollars per user??).