Explain the reasons why management might choose a direct approach to a system changeover in preference to other alternatives (such as phased, parallel running or pilot schemes). 

Low risk

The system may be already widely used elsewhere in competitor or comparator organisations (it might be an 'off the shelf' package). Under these conditions, management might be have complete confidence in the system.

Low cost

Management might be have weighed the options (such as phased, parallel running or pilot schemes) and concluded that a direct approach is more cost well-organized in terms of time and resource usage.

Symbolic gesture

Management may wish to communicate to the workforce its commitment to a certain system and the direct approach shows a symbolic act confirming its faith in it.