Normally Use Case Diagrams are used but the pictorial information in it is so small that an MS Word Table is sufficient. What is more it can also provide space for "Use Case Goal" which is very important for Use Case Modeling.
Tables are quick and easy to create and edit. No need to waste time to draw and label diagrams. One can still do it if necessary after creating the Use Case TABLE. Try.
A Use Case Table can spill over into multiple pages but a diagram cannot!
UML 2.5 allows TABLES to be used for diagrams. So, there is no compulsion to create diagrams spending a lot of time.