The replacement system must have most of those refinements in place at the beginning or many people will conclude they have taken a step backward. The difficulties caused by complexity and customization are magnified when the shortage of resources is taken into account. Cutbacks, reorganizations and mergers have typically left laboratories without extra resources to apply to major projects and the LIS installation suffers as a result. If all of these modules are now part of one system, that system will more than likely have to be replaced over a very short time frame. All departments must be up and running on the new system at precisely the same time.
Systems are easier to replace one piece at a time - and the smaller the piece the better.
A third complicating factor involves data conversion. Blood Bank and Surgical Pathology were exceptions but even these were entered gradually - typically when a patient returned for testing. Most users today require that critical databases be converted before going live but incompatibility of databases makes this extremely difficult. The fact that a given vendor will replace only a very few systems of a given brand discourages that vendor from developing sophisticated conversion tools. The situation is even worse when the system being replaced has little or no support from the original supplier - possibly a reason for the replacement.