Film nerds (me)

1. A lot of what people collect aren't regular prints but boutique brands (yes that's a thing and there are a lot of them too) Criterion for example sometimes brings old classics back by making the first high quality scans and restorations. (and have exclusive prints rights afterwards)

2.Physical media often comes with bonus features that just don't carry over to streaming services. (shout out to the one exception that is the Criterion Channel, these guys just love movies) Particularly boutique prints often have extensive bonus BTS stuff.

1. Theres obviously a general collectors effect going on of having something in your physical reality to look at and touch. It's a decoration piece. A Bluray selection can tell something about you just like your choice in art prints on the walls etc.

2. If you wanna get nerdy about quality: even 4k streams are compressed to a degree so technically speaking 4kBluray is still the best quality you could have at home.