For me there are several factors in play. I have a pretty big digital collection but not massive by some standards. 9,000+ albums or 115,000+ tracks according to Roon. Somewhere around 8-10TBs. In no particular order here are the reasons I feel for my obsession.
I remember a day when I was young and poor and had to agonize over which single LP to buy with my meager savings. Typically I got Greatest Hits LPs, like Made in the Shade by The Rolling Stones. Then always regretted not having the complete album. When funds allowed as I bought the original albums and always swore once I could I would always buy the full album.
I’m a bit of a completest. If I like a band I want all their stuff even if I don’t really care for some avenues they have explored. I think this stems from days of going to someone’s house that had a huge display of LPs and being wowed. I love the days past, of looking through others LP or CD collection. “Oh if you like this you gotta hear these guys”…and the like.
I’ve bought and rebought albums, some several times. Sold LPs to fund the latest craze of CDs, Sold CDs to fund other CDs and regretted it. Car broken into and radio + large CD collection stolen…in the days before CD burners for travel copies. Digital + multiple backups hopefully solves that.
I have always been the guy with travel tunes for the train, beach, vacation house, etc. and the same when people come to my house. I like to have something on hand for everyone even if I don’t care for it.
I live in the middle of nowhere with limited internet and data caps, so no streaming of any kind.
I’ve discovered Swap a CD and Music Boomerang that are CD swap sites. Literally pennies for CDs so I collect them and rip them to my NAS and throw the CDs in a plastic bin. Various artists CDs are a great way to find unknown to me bands. This recently happened to me with Pell Mell. How in the world did they escape my orbit back in the day?
I’ve got some rare stuff that is not available on streaming sites even if I could stream.
I’m no longer poor but remember those days, so I tend not to get rid of ANYTHING. Yes I have some Dolly Parton that I’ll never listen to, but maybe just maybe I will find it by Roon Radio and like it, or someone will come over that wants to hear it and we can’t “stream” it. Side note - I’ve had multiple people come to the house 5-10 years ago and when I did not have something “I just had to hear” I was forced to listen to it at full blast on their phone. YUCK!
I have a tablet loaded up with Roon and people love hanging out while my wife and I are cooking and play DJ.
EDIT: Forgot to add that l like to have multiple versions of albums I like or that are particularly well recorded/mastered. I’m a sucker for MoFi, 1/2 speed masters, remasters from original tape, SACD remasters, etc.