I agree, this is really annoying. I work irregular shifts and would like to be able to quickly drop them into my iPad calendar so I can plan my month without being dependent on paper diaries and calendars. You can copy-and-paste like this in Outlook. In the new iOS5 calendar you can move events within the month view by dragging them, but not copy them.
You could look at some alternative apps like SmartPad and Pocket Informant, I have both and they are highly configurable with good support from the devs.
Free apps are always likely to be less powerful than paid apps.......I've not come across your issue before so I'm guessing that it isn't a much requested feature however, you can leave comments here http://www.apple.com/feedback/ipad.html and maybe Apple will consider adding it as an enhancement.
The updated calendar now has better interaction capabilities with events, you can drag them to other dates, increase/decrease the time by dragging etc, very nice additions!
I was trying to work out the same thing. If you go into the monthly view mode of the calender, you can drag and paste into the day you want to repeat that event, so saves u have to type it all over again each time
Cocosabi, could you you describe exactly how you are doing that? I can drag an event from one day to another (cut and paste) in monthly or weekly view but I cannot copy and paste. If I drag an event it is removed from the day I was dragging it from.