I agree with you about them being the most enjoyable days.
And I also think you demonstrate the point about prelaunching. If players weren't around in the early hours of the morning then they attacked at different times - thereby adding a bit of variety and a bit of excitement during the daylight hours.
Another benefit of having to be online in order to launch is that we're (more) likely to talk to each other while we're waiting for launch time to arrive. With PL we can just pick our target, pre-launch and go to bed - not much contribution towards the community spirit there.