I think Dave does a pretty good job explaining why some teachers might want autofill, but I'll give another scenario. At the high school level and below it is actually quite common for teachers to give whole-class "did it/didn't do it" type assignments and for teachers to use the gradebook to communicate with parents regarding the completion of these assignments. The points are usually fairly trivial, but the column serves as a marker that will help to explain gaps in homework preparation for quizzes, etc.
When you have 65+ students doing the same assignment, it is easier to autofill full points for all and adjust the few lates/zeros individually than it is to manually type/select the same drop-down points 55 times for those who did complete the assignment.
Personally, I always typed the numbers in anyway as both methods are fraught with places that could generate possibilities of human error either way. I think that the autofill might have prevented me from making a decimal error I made for one poor kid once, though, when I accidentally gave him .5 on an assignment instead of the full points (this was using our school gradebook, not Moodle, but you get the usability picture).
Regarding the reason one might want the ability to copy assignments into several courses, this goes back to how some may or may not be choosing to use grouping
structures within courses. I chose to use groups within one course so that all of my English 9 courses met in the same course, but had their 4th hour/5th hour/7th hour designations using groups. But some cannot use groups because they have enough level differences between curiculum in their 4th and 7th hours, for instance, that they don't want everyone in the course to be able to see all assignments and compare. They choose to do separate "courses" for each "section" (which is, essentially, a group--more or less the same curriculum/level, but with slight variations). At the same time, there is a significant amount of curriculum that is shared that they do want to be able to copy.
There is, of course, the import function for in-course activities, but for those assignments that might just simply be added into the gradebook--not part of the online part of the course, there is not currently an easy way to copy from course to course. At least, I think this is what she is saying... Emma, correct me if I am wrong.