These days it's mostly sentimental value and "too cool to throw out", for me. A lot of stuff old and new, mostly the unique/cool packaging (Mini-con multipacks, United box sets, Takara exclusives Throne of the Primes, Arcade Renegades -- kinda want to find a second copy of that last to keep sealed, really), stays mostly on the merit of the latter. Although of course the acquisition encounters may have sentimental value too.
Beyond that, I do still keep at least the cardbacks, as I have since the beginning. But I get the sense that the appeal of the latter will either fade or abruptly disappear one day and it'll be a massive culling in this house.
(Helps that I've been scanning packaging into digital form for a while now. I do need to redo some older ones because the scanner I used for that was on its last legs and so there's horrible banding on everything it touched. But alas, I'd thrown out most of it.)
The Selects boxes were a nice little vacation from being tempted to hold on to things, as aside from Bug Bite and Tricranius and the Galactic Odyssey boxes they were nicely generic. Of course Legacy Selects has straight up undone that.
The days of packaging meaning literally anything in terms of adding value to stuff are long gone. Collector circles here will still murmur about keeping the box for value and whatnot, but try to sell anything (boxed or not) and people will haggle like crap regardless, so I stopped doing that a loooong time ago.
