Now, can you guess why most of system and network administration programs (like in UNIX, Oracle Database Server, etc.) have a command-line interface?
System administration tasks often are performed in the conditions, where many resources are unavailable, for example, after system crashes or faults. Even if it is not the case, it is preferable, that these tasks slow the overall performance of the system as less as possible, which leads to the choise of a "cheap" interface.
Further, system administrators usually are well trained and experienced computer professionals (at least, they are supposed to be). For this cathegory of users the flexibility ot the interactions is crucial for the performance. The tradition is another important factor.
In the last years some vendors started to develop and include additional administration tools, which use direct manipulation. Nevertheless, they still keep the command line interface.
This example shows again the importance of the user group analysis.