Today's example: The World's Most Useless Cat (stuff like this)
There are a bunch of these types of pictures out there, but the general theme is a cat who is just hanging out with a mouse instead of killing it.
Well, duh. Most housecats were never taught how to cat Hunting isn't just an instinct. It's also knowledge. In the wild (or in the case of a household who is keeping them) they're taught by their mothers, starting from the time when they're weaned. That's about the time they're usually sold/given away.
The training they get as they're raised by humans is to be gentle, to only damage things like their scratching post and their squeaky toys. So why would you expect them to go hog-wild on an actual fuzzy living creature?
That's not to say many of them can't pick things up fast if you let them outside and give them some time/motivation to figure it out. Many of their "play" behaviors in the house are limited or unfocused pieces of the art of the stalk. The instincts are still there, and hunger is a sharp sauce.
But you don't take a kitten who comes from a line of probably generations who have been born of mothers who never have left a house and were never taught themselves what to do and who has been taken from that mother just when it's time she should start showing them the ropes and expect it to act like a slavering beast just because it's shown something from the order Rodentia.