One use case is the following: Review of issues for a defined target version.

First a static filter is first defined with the list of issues.
Then, with the dynamic filter we can review the status by assignee for example.
Although the second filter could be also done with static filters, if the number of assignees is high, we will end with too many filters. If we have many versions (and many assignees), the number of static filters explodes.
An option would be to edit and modify the filter, but it is not efficient at all.