Some rentals are cheaper than Starbucks, but many new releases are $5-$6. Also, I frequently find that a movie I'm looking to rent on iTunes is only available for purchase ($15). I understand why studios push for these sort of arrangements, but since there aren't any brick and mortar rental locations anymore, it means there isn't a way to check out that movie for less than $15.
It's hard to argue with the convenience of free and immediate, that's for sure, but it's really hard to care that a person craves entertainment so strongly that they feel their unwillingness to pay for it is somehow a compelling argument to take it.
No studios will collectively give a tech company the majority of the licenses to make this possible - so torrents it is.