That just shows you that convenience is important to even you. I can purchase a video on iTunes, on Netflix streaming, or on Pay-Per-View and have them all start playing right away. If I had a such a slow internet connection to wit I could "drive to the store and buy a real copy faster than I can get to watching a crappy iTunes copy” then i would likely be going to the store to rent my movies instead of use these inferior in quality yet vastly faster (for me) options.
Maybe I'm remembering it incorrectly, since I do not have a slow internet connection. Does the Apple TV have instant playback upon rental/purchase? The xBox's rental system required waiting until the movie had downloaded to a certain point; I tried both of them out briefly before signing up with Netflix.
Convenience is absolutely a factor, I don't disagree. But with the way the distribution rights work for movies, digital rental or purchase is not a one stop shop the way it is for music. The inability to rely on iTunes or your cable provider for all of your movie needs (you don't know what they'll have or if they'll still have it the next time you check) makes it an inconvenience compared to Netflix or Blockbuster, who will undoubtedly have the movie I want and in the highest quality available to date.
I rent from Netflix; it's cost effective and there's not a movie they don't have. Sure I can't have a movie instantly, but if I can't stay on top of managing my queue and mailing movies back I'm probably too busy to watch a movie anyway. I only buy the movies I want the most, and pick them up at the store on the way home the day of their release. Can't get a whole lot more convenient than that.
Now, if I knew I could rely on Apple to have the movie I wanted streamed to my television in Blu-Ray quality for a low monthly subscription fee, of course I would be all over that. But with the current pricing, quality and selection it doesn't make a whole lot of sense.