Legally, I think they usually make a stricter claim than that: You are purchasing access to the content, but only using the method that you paid for. If you buy the DVD, you aren't licensed to rip it and play the content from files (unless you live somewhere with medium-shifting laws that provide that right).
Further, say that you own a copy in some format, and you torrent an equivalent quality copy. What they'll actually go after you for is the redistribution of tiny chunks of the file to other people in the torrent swarm, because it's easier to prove that you took part in unauthorized redistribution than to prove that you didn't have the right to access the content in the format that you torrented.
Oh, and the ability to keep my kids tablets in airplane mode (triple the battery life!) and still let them watch their favorite shows/movies on a long road trip is definitely worth the extra effort.
There also are many smaller details that makes torrent more attractive, like being able to watch the movie offline, HD with low bandwidth, subtitle choice, etc.
Netflix is a good step, and of course the movie industry will use it as "no excuse" argument against piracy. Meanwhile you still have other issues about net neutrality and people using VPN when they can.