Often, because in the calculation of the provider, one factor never appears. Training-time, if a superior tool comes along, making it necessary to retrain to do

Often, because in the calculation of the provider, one factor never appears. Training-time, if a superior tool comes along, making it necessary to retrain to do the same work, its not superior, its inferior until the gain is so big that the productivity loss is visible to the customer. That is why even with superior software it is necessary to add a "Legacy"-user interface, that allows for a easy switch from old software, while at the same time retraining people to use the new interface. This changes the transition costs.