An array {{ value }} doesn't display.

I loop through a collection that has an image array:

alt_covers:
  - path/to/image.jpg  
  - path/to/image.jpg  

On the front end, this code works:

{{ alt_covers | ul }}

BUT the below code does not work:

{{ alt_covers }}{{ value }}{{ /alt_covers }}

Watch this video for an demonstration: video demo

What am I missing?