When all the good shows were on cable, we still kept our cable subscriptions even after we bought our favorite shows on DVD or blu-ray. Well, many of us, anyway. The only reason I had cable at all was to watch Mad Men. So once the show ended, I immediately canceled with no regrets. It was expensive to have cable just because I liked one show.
Personally, there are certain shows and movies that I want to have on pristine physical media because I like them a lot and I want to enjoy them in the best possible audio-visual presentation, without dealing with the hiccups of streaming, internet outages, the first minute of every show looking like garbage while it buffers, possible losses of licenses, etc.
On the other hand, there are dozens of other shows on the streaming service that I find entertaining enough, and I will gladly watch, but I don't want to own physical copies. And other viewers may buy some of those particular shows on disc, but not buy the shows that I personally like. So it's well worth it to keep paying the $6 a month for the service even after paying $40 or so for a season set of one particular show on blu-ray. If I get The Mandalorian and WandaVision on blu-ray, then the Mouse just got a lot more money out of me than if I only had the streaming service. And besides, I cancel the service between seasons of shows that I enjoy. So they lose the revenue from my subscription during those times.
Kor