Titles leave streamers all the time before I get around to watching them.If I can watch what I want, when I want, on a service which is obviously not going anywhere, then logically speaking it's irrelevant whether or not I "own" what I'm watching.
Besides, with iTunes, it can be argued that I really DO own it! They don't even charge a yearly fee! So once I buy something from them, I'm in the clear.
Edit: Just so you know, I'm talking about iTunes, NOT AppleTV+. That's a different thing altogether.
Streamers often do not have director's cuts / special editions, which I prefer.
Streamers usually have few to no "special features," which I value as much as the film itself.
Even with things like iTunes, you do not own the title. If iTunes loses licensing rights, I believe you lose your "purchased" titles. I have heard stories of this.