I do generally believe that the ability to run a 5k is important, but "reasonable time" has a shitton of wiggle room. Maybe it is me, but I find cardio easy to develop and quick to be lost. I feel like the people you are laughing at probably have an extremely strong base to train a sprinted 5k on if they wanted to. The question would be, without a sport to entertain you, why would you want to? With my limited time and recovery ability, I have elected to work on adding 20lbs to my bench as opposed to stripping 20 seconds off my 5k.