I like this because it speaks to our compulsion to personify the non-human and wrap stories around them, seeking meaning and a means to connect where oftentimes there isn't any.
Obviously this is an ad, so there is clearly a message that's constructed and conveyed, and you are meant to sympathise with the cartons of milk. (Something new to discuss in therapy!) Still, as the video progresses you can literally feel your brain trying to catch the cues: here you're supposed to see a face, there a flirtation, here a kiss.
This work you do of completing that web of meaning in your mind is sometimes just enough to justify a bond.
The ending is easy to guess well before, but I like how it concludes by leaving the viewer with a sense of agency over the tale instead of giving you the flat, too-easy "...and this is why you should...!"
By Catsnake for Friends of the Earth, UK. The website could be more engaging, especially now that I'm all emotionally invested in two empty estranged cartons. FOE, you could've turned that call to action into more than a mere flirtation with agency. You could have directed the (now primed) energies of those who want to change the story and save the world.
(Consider the Rainbow Warrior.)