Comment by Springtime

Pirating doesn't help sustain the very thing being pirated, if you want a tangible rather than moralistic reason.

4K (Ultra HD) Blu-Ray is likely the last physical home video media generation to be produced. Disney has pulled physical out of the Asian market, Best Buy stopped releasing any physical media beside games, Target stopped selling them beside certain DVDs.

If you want any chance of actually having high quality releases continue it needs to be supported. An issue though is certain less mainstream releases in Ultra HD Blu-Ray can be rather pricey (if they get a release at all). However I still buy those I'm interested in since I don't want lower quality streaming-tier video to be the only option available in the future, apart from concerns about the volatile nature of online-only libraries (various of which have been wholly removed in the past when licensing/ownership changes).