VBA scripts are especially good at completing large, repetitive tasks within a document. If you had a Word document with a very large table, and you needed to modify the contents of each cell to reflect a different value or set of characters, you could perhaps save time by using a VBA script. Additionally, and perhaps more importantly, VBA can be used to provide a level of interactivity not present in documents created without VBA scripts.
For instance, a document that is used to tally the monthly materials costs in a small cabinet shop could include a script that reminded the person opening a document to include any carryover expenses not accounted for in the last report. Or perhaps a certain employee always forgets to bill their accounting time under a different labor code than the code used for their standard administrative duties.
VBA code could be used to create and display a message that said, "Please remember to bill accounting hours under code 903," every time an accounting-related file was opened.