At present, the PPT export option isn't available. I'm afraid it's unlikely that we'll introduce this feature anytime soon.
The corresponding suggestion ticket is still marked as Accepted - TBD, which means that we have not established any release date for this feature: Export - Add a new export format - PPT (Power Point). As an immediate solution, you may use the approach described in the following thread: Exporting report to powerpoint. Hope this helps.