The reports provided in CalDAV can be used by clients to optimize their performance in terms of network bandwidth usage and resource consumption on the local client machine. Both are certainly major considerations for mobile or handheld devices with limited capacity, but they are also relevant to desktop client applications in cases where the calendar collections contain large amounts of data.
Typically, clients present calendar data to users in views that span a finite time interval, so whenever possible, clients should only retrieve calendar components from the server using CALDAV:calendar- query REPORT, combined with a CALDAV:time-range element, to limit the set of returned components to just those needed to populate the current view.