I can bet you it's incompetence. They failed upwards. Sure, protocol is great and universal, but connector is atrocious and it has nothing to do with cost. Few points in favor of this hypothesis:

1. Plastic inside of the connector was initially black. Why chose hard to see color? Go with something easier to see;
2. Connector is perfectly rectangular and only distinguishing feature they made hard to see. Don't make ti symmetrical if it's not reversible, basic design principle;
3. Connector is perfectly rectangular making it difficult to insert. There's a reason why most connectors have rounded corners, they are self-correcting, even TypeC does this;
4. They made various different connector types but pushed for the only one with these issues. No one ever had doubts how type B or mini B or micro B go in.

New question: why did it have rotational symmetry?

Considering the much higher cost of production then vs now, it makes complete sense. The economy of scale took care of that problem with time.

Usb-c gang

The picture explains itself. The cable exists in a 4-dimensional space.

It doesn't necessarily need to be 4-dimensional https://en.m.wikipedia.org/wiki/Spinor

I really wish hdmi was symmetrical. (Peer behind tv, “which way goes up?” Tries to plug it in, “fml it was the other way” flips it drops it)

Honestly, with high quality USB A plugs you could feel the logo on the side that was "up", and if you knew which side your motherboard or front panel considered "up", it'd be easy to always plug devices in correctly.

Just that the vast majority of manufacturers stopped caring relatively early on, which meant you couldn't rely on it anymore.

They're supposed to label the USBs so that you can tell which side is the top side and which side is the bottom side.

The problem is that, A they often don't label them and, B I can't remember which way round it's supposed to go anyway, so it wouldn't help.

Perhaps a controversial opinion here, but the usefulness of reversibility is vastly overrated. It's not a game changer, just a tiny first-world luxury that's nice to have, but it does it by introducing a bunch of unnecessary complexity that I'd rather avoid. Not worth the trade off IMO. I can count on one hand the number of minutes USB-C has saved me by being reversible and I honestly don't care

1. Attempt to plug in the USB A device
2. If you succeed. End procedure
3. Otherwise, destroy the reality you currently reside in. All remaining universes are the ones where you plugged in the device on the first try.

That wasn't so hard, was it?

For USB-A, it's usually not even 50/50. It's the witchcraft superposition when the first two tries don't work.

USB-C has more connectors for data and power than A/B so it's not a surprise that it's more capable.

What's really changed is demand. No one really expected USB to be used to power everything, it was only ever really expected to be used on computers and maybe digital cameras, smartphones used to arrange matters for themselves. It was only when they two began to adopt USB aas well that calls for smaller ports and higher capacity cables started to arise.

Circular isn't a great idea, and here are most of the idea why it is not : https://electronics.stackexchange.com/questions/528821/why-dont-we-have-a-circular-usb-port

USB required to have a stable connexion, as it's a digital signal and not an analog as jack ports, which just sends curent through it. Rotating the connector could maybe introduce issues for signal integrity.

The usb connector has much more connectors than a jack port. It would take a very long hole to fit them all. (usb 3+, usb C...)

Size constraint. USB C is flat, a round port is not. So it's bigger in 1 way, but smaller in the other, and so creates more design challenges.

Almost all connectors in use on computers at the time USB was introduced were already keyed, and a fat lot of good it did us. Ask anyone who tried fumbling around behind a three ton CRT monitor or computer case -- even with the keyed connectors, feeling for which side was up, getting anything plugged in without eyes on it was already nigh on impossible.

What the USB A connector did do which was new at the time was introduce a connector that did not have any protruding pins on either the male or female end, and thus theoretically at least could not be damaged by fucking up the insertion. Unlike any of the then-common D-Sub connectors (VGA, serial, parallel) or DIN (PS/2 mouse and keyboard, Apple serial, S-Video, etc.). USB didn't even have the little clip to breal off like an RJ-45 Ethernet or RJ-11 phone line connector.

Circular.

The PS2 (and AT) connectors keyboards and mice were largely using before USB were round…

Arguably still better though because you could just rotate the plug until it went in instead of flipping it back and forth 5 times to get it to go in. And they also had more reliable indication for orientation.