The option to crawl under the obstacle is invisible to the cat until it estimates it cannot make the jump. I think there's a life lesson here, but I'm still hung over.
Presumably that comes with increased risk (of e.g. being eaten by predators) in the wild. The life lesson would thus be something along the lines of "stay on top of the situation at all times".
I just tested this with my cats. Cat A went through the tape ripping it off the wall in the process. Cat B ran away from the noise of the tape coming off the roll and then just walked around to the other entrance.