I have my copies of Halo: Reach, 3, 3 ODST, 4, 5, and a windows XP copy of CE for two reasons: in case I play them through backwards compatibility, with or without someone, and to look at nostalgically on my shelf. But… they just sit there collecting dust.
Anyone else just get rid of theirs except for maybe Halo 5? Its like the books; I love buying and reading them. I have a hard time using audio books and I love seeing collections on my shelf. But after awhile of not re-reading most of them, I feel like selling them all. At that moment I do want to reread them over time.
With books I enjoy seeing them on my shelf, trophies for the journey through them. With game jewel cases, I’m not as captivated by. I play most of my games digitally so I’m not popping them in and out any more. With switch games I do enjoy seeing their jewel case, they are compact and fit nicely on a shelf. Plus the spine art isn’t just the same font, and text like it is for Xbox One games. I guess for me Im pretty split.
I still mostly buy physical just for the reason I like having a collection to look at. I got basically 1/3 of my shelf with all the original Halo games as I got pretty much every steel case including the fat Halo 3, 4 and Wars cases. So it’s pretty safe to say I won’t get rid of them. The only one I don’t have anymore is CE anniversary as my doggo decided to chew that one but I’d honestly just go to mcc if I want to play anniversary, it just plays way better.
If not to play them, I just like looking at them and getting a rush of good memories playing back in the day if nothing else.
I think there’s something special with having hard copies of games from older generations. Yeah, I might not use the hard copies as much with easy access to the mcc, but I still enjoy booting up the older versions of the game to get that rush of nostalgia and to appreciate how far halo and the rest of gaming has come.
I have a bookshelf dedicated to all of my Halo games, books, movies and collector’s edition statues! 
Shoot I forgot I made this thread.
I like seeing the journey too. Sometimes I pull a book out to glance at a page. Once in a while I re-read one. The old games I never use; they are there for looking back and smiling.