A lot of local rides, whether it be events or just random club rides or just some friends going out for a ride start around 6-7am so early morning starts aren't unusual over here. Due to the climate in equatorial countries we generally want to start early and minimize time under the sun... though when it comes to randonneuring I guess that is a moot point. It's just when it takes 2++ hours drive to get to the starting point that it starts becoming an issue.
My most recent 600k started at 1am, 3 hours drive from my place, which was a new record of WTF for me... but considering the heat wave going on at the time, and the estimated time that most riders would reach the 300k mark, was a pretty good strategic decision that helped us stay cool for a longer time, and get riders within civilization before it got dark.
An upcoming 400k is going to be annoying though. 6am start, so pretty reasonable, but depending on traffic 4-5 hours drive. Ugh. I know there are people who can take 2 days of leave for an extended Friday-Monday weekend off work for this, but not everyone is that lucky (or free of any other sort of personal or family obligations to get that kind of time).