This one line from the linked article made me laugh: "It is one of the most fondly remembered of his 'juveniles,' perhaps today because of the connection to tribbles"
And George Washington is famous because I wrote a biography on him. (Actually, I haven't, but you get the point.)
Actually, though, the Heinlein story probably is
better known today because it inspired, consciously or otherwise, one of the most popular Star Trek
episodes. Same with Frederic Brown's "Arena."
I mean, how many people would know of Arthur Clarke's short story "The Sentinel" if it hadn't been the basis for 2001: A Space Odyssey