Why can't I turn an iTunes movie rental into an actual purchase yet?

I rent a lot of movies on the Apple TV. It's quick, it's easy, and new titles are available immediately upon release — if not sooner sometimes. Usually that's fine. I don't often watch a movie more than once. Sometimes, however, I like a movie so much I decide I want to buy it. That's when things get interesting...

I prefer buying movies from iTunes over any other service. It's just so convenient. We have Apple TVs in almost every room of our house and so we can access anything we rent or buy regardless where we are in the house. When traveling we can access it all through the iPhone or iPad, and we can even AirPlay to our friends' and families' Apple TVs when visiting. iTunes in the Cloud is really a great system. But I do wish it offered more when it came to renting vs. buying.

A debate typically takes place in our house just about every time we sit down to watch an iTunes movie on the Apple TV — should we rent it or buy it? It's not a debate I like having but it's a necessary one given the way iTunes currently handles movie rentals and purchases. "Am I going to be pissed at myself for buying this movie if I don't really like it?" vs. "Am I going to be pissed at myself for renting this movie if I like it so much I want to buy it?"

If I do pay the average $5 to rent the movie and then decide I like it enough that I want to buy it, I then have to pay the full average $20 price to do so. Unlike "complete my album" which lets you buy a song and then, if you decide you want the rest of the album, get it at a reduced price, there's no similar incentive to convert a rental into a purchase.

Imagine if there were — you just finished watching a rental and a you get a popup saying it: "Love this movie? Own it now for $15!" or something similar. Maybe even $16 or $17 so the movie studios get something extra out of it as well but we still feel encouraged to "upgrade".

It would also solve another problem. Currently you can't buy something on the Apple TV until after the rental period expires. You get a play button but no purchase button. So, you either have to go to iTunes on the desktop or wait and maybe forget you wanted to buy it. Neither are huge problems, but they are inconvenient and barriers to converting a sale.

I have no doubt studio licensing agreements could be the reason why movie rentals can't be converted into movie purchases. We still live in a time where movies come and go from iTunes and other surfaces based on archaic "broadcast windows" and sometimes even movies we've purchased can't be re-downloaded, at least temporarily, thanks to the studios.

Apple has shown they can help the studios grope their way towards better customer experiences, so hopefully they can work similar magic here and get us the ability to convert iTunes rentals in purchases. Because, take my money.

Do you find yourself debating between rentals and purchases as well? Would you like the ability to rent first and upgrade to a purchase later?

UPDATE: Want to let Apple know how you feel? If you've got a developer account, dupe the radar in this comment below!