Let’s say The Mandalorian lasts 4 seasons. Who is going to subscribe to Disney+ solely because of The Mandalorian after that? If they want to get more money out of that show, the only way is to make it available on physical media. If they do that, do you really think they would lose subscriptions at that point with 37 new shows coming up already?
That’s the point though, they keep adding new content to keep it going, but let’s say someone hates the new show but still loves Mando: they’re more likely to keep D+ (especially if there’s one other thing they’re curious about it enjoy) if there’s nowhere else to get it.
Years after it’s finished? Unlikely, or just unwise.
People subscribed to Netflix for years and only watched The Office and Friends. It’s more common than you’d think… and the people who don’t want to rewatch the show won’t be buying the physical media anyway.