I don't know what it's like in other countries, but here in Australia you need to get permits from the various state/territory governments to run a competition like this, and they all have different requirements. It can take several weeks to get all of those permits through because the lodgements tend to take about a week to be processed after which you may be asked by some states to adjust your Conditions of Entry and resubmit your request thus setting you back another week.

I imagine running a global competition would be a serious pain and take a long time to organise if they had to lodge paper work like that in every country.