I am certainly a digital pack rat. Luckily, unlike physical pack rats, our data doesn't take up a lot of room, and since storage capacity keeps increasing so rapidly, I have never had to delete anything.
Here are some of the things that I have that add up to my multiple TBs of data I want to keep around.
First, I have every single school assignment from growing up (30+ years ago, so it doesn't take up much space). These are kind of fun to have. I can show my kids the papers I wrote when I was their age.
A lot of old converted 8mm tapes from when I was a kid. I used to be really into making claymation videos, so I have hours of videos that I converted around 15 years ago into digital formats. I could probably reconvert them to a more modern codec that would take up less space, but they are still multiple hours. Currently takes up around 100 gigs.
Every digital photo I have ever taken. Over 20 years, this is a lot of photos. A few hundred gigs there.
Tons of videos of my daughter. A hundred gigs there, growing all the time. Maybe I take too many, but it is really fun looking back and remembering when she was little.
Every programming project I ever created, going back 25 years. Fun to see my progression. Not a ton of space, but many gigs worth.
A ton of old games that don't exist to download. Old shareware, commercial games, etc. I created CD images for the all the ones I had on physical media, so I don't have to lug around the CDs anymore. I like to be able to play games I played years ago every now and then. This takes up a good chunk, and is probably a few hundred gigs.
Ripped DVD movies and TV shows. Bought many over the years, and don't want to have to find and/or rip them again if I lose the data. This is hundreds of gigs.
Countless other minor things (saved games, documents, etc).
I like all of these things. If I have a house fire, I like knowing I wouldn't lose all of that. Since it is so cheap to maintain a backup of it, why not? Yeah, I wouldn't be DEVASTATED if I lost all my old DVD rips, but for 60 bucks a year (and that is the same cost whether I back those up or not), why not keep them backed up?