How’s this as a reason for round manhole covers? ManHOLEs are round, so the covers were made round to fit the hole. The same round pipes that run underground are used to create the access points known as manholes. Once a round manhole cover was in use, we all discovered that they had other advantages, such as not falling in, rollability, no corners to line up, no corners to pop up when a car goes over, etc.
Not to mention that the entire purpose of the holes is for mankind to go down them. People are round in horizontal cross-section, to a reasonable approximation. It’s simply a more efficient shape, anything else would have to be larger, for no good purpose.
And, finally, manholes are round because its an inherently stronger, more pressure-resistant shape.
Haven’t read the article in question, but the OP’s premise is off. The pipes that run underground are rarely used “to create the access points”, many old manholes were, in fact, square, and many of the old ducts that were used to contain different wires were also made of wood and square.
After reading the article in question, it looks like Cecil missed out on the fact that round as a standard seems to have been, to some regional degree at least, a matter of trial and error.
I’m not a manhole expert, but I worked for a company through college that was subcontracted to do line work for the phone company (Nynex at the time). I came across several extremely old manholes with square covers (even dropped one in the hole once), and even more old square wooden ducts that were so rotted that attempts to feed a snake through in order to pull new lines were impossible.
This is north shore Massachusetts, for whatever it’s worth.
Maybe Smoke’s manholes were square and so the covers were square. But that sorta supports my point. Square hole, square manhole. Round hole, round manhole. I never worked in a manhole, but I see the pipe (or whatever you want to call it) that is delivered to worksites in Chicago that is used to repair the access points. It is round. I’m just saying that, if the hole is round, you might be inclined to put a round lid on it. Same as most hats are round to fit on round heads. Sure, some heads are square, but then you’d probably use a square hat.
I think I’m being whooshed, so sorry (for myself, maybe?) if I’m coming across like a nerd here.
I’m just hoping that there’s a little more planning involved than one team making manholes, and then another team coming along and doing a Sesame Street-style match-the-shapes game in order to find the right cover. 
Whether you’re entirely serious or not, I thank you for briefly making me feel like a character in a Dirk Gently novel. I’d definitely be interested in hearing about your method for navigating on car trips.
No one is saying that the “round” manhole cover was invented by someone precisely because of all the advantages one has, as outlined in the article. What they are saying is that the preference for round manhole covers exists for the reasons given in Unca Cece’s article.
Ever tried a square butt plug / man hole cover? No wonder they are now round.
He steers using his hands which are made the way they are so they fit steering wheels.
Look, it’s simple: Manhole covers are round because the manholes themselves are round. You can’t put a square cover over a round hole. Duh!
So, why are the manholes themselves round? Because the round manhole covers wouldn’t fit otherwise. You can’t put a round cover over a square manhole.
Now let’s get back to discussing something important like if an airplane can take off on treadmill.
In the article, “Reuleaux triangle” is misspelled.
I also deemed it necessary to put out that there is no such thing as a rouleaux triangle, and what Cecil is actually referring to is the Reuleaux Triangle.
Well, except that the vaults themselves-- that is, the little underground rooms that the manholes lead to – are bigger than the actual access hole. Kind of like your living room is larger than your front door. So there’s no clear reason for the access hole to be the exact same shape as the vault; kind of like your living room is wider than it is tall, but that doesn’t mean your front door is wider than it is tall.
Does a fake Rolex by any other name smell as sweet as a sewer?