I understand that it's not necessary. I just think it would make an interesting framework for a continuing series of games, rather than just a one-off. It lets you continue to current story of the universe alongside that of the past, so you can keep the Halo story moving forward in small ways even while we explore these events from the past.

Also, there's a huge part of me that rages against the trend for prequels set by Star Wars and other similar films/media. In my mind, prequels should be handled as flashbacks (if anyone's read The Dark Tower series, King does a great job of this with Wizards and Glass), that way fans never have to go through this debate of what order to go through things with people who've never experienced the story before.

Do you play Reach first, or do you play Combat Evolved first? The problem is, if you go from Reach to CE, you won't enjoy CE as much because it will feel like a step backwards in quality. That's jarring, and can get in the way of your enjoyment of something. Stories should always be a gradual progression, getting better in quality as you follow it through.

If someone who knew nothing about Star Wars were to just follow the series in its numerical order, they might not enjoy 4-5-6 as much because of the dated effects. The proper way to do it would have been to leave the first trilogy as 1-2-3, then introduce what we know as the prequels as 4-5-6. Episode 4 would start with Luke going to Dagobah or some remote Jedi planet to converse with the Force ghosts of Yoda and Obi Wan. Obi Wan's ghost would begin the narration ("When I first met your father, I was a Jedi apprentice, serving under my master Qui Gon...") and then the rest of the movie would proceed as we know it. But at least with that framework, you have a clearer sense of the order you should watch things in, and you'll never have to go through jarring shifts in quality.

Some of this is just me expressing my wish that Halo could rise above the conventions we currently have in film and games, stop focusing only on the current audience, and think about people who will play the games in the future and what that experience will be like for them.