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You've all probably experienced this at least once: trying multiple times to plug in a USB stick correctly, because somehow it isn't intuitive what side goes up. This is especially the case when the USB stick in question hasn't been yet used by the user. But it can also happen with sticks that the user is already familiar with, as confirmed by the experience of the writer of this post.

Here are some pictures that illustrate this common experience.

So what's wrong with the design of an USB stick that makes it not intuitive enough to plug it in correctly the first time?

In my experience a USB plug needs a bit of pressure to go in the port. It’s enough pressure to make me wary that I might break it if I’m putting it in the wrong way.

After reversing the plug, it becomes obvious that it does not fit entirely. This observation allows me to flip it again and now apply more pressure with confidence.

Short answer: Design commonly causes misalignment

Most plugs or ports have a flared edge, beveled plug or some other design that allows for the orientation of the plug to be slightly off and still match. USB doesn't.

Oftentimes, the first attempt will cause your plug to be aligned too high, slightly twisted, or some other orientation that doesn't allow it to go into the jack. Most USB ports are surrounded by plastic, where you might have the plug touching the edge of the plastic at some corner, and you assume you had it upside down. When you flip it, the fiberglass circuit board edge inside the plug hits the fiberglass circuit board in the jack. This causes the plug to shift to an angle up or down, and you are certain it is upside down. Now when you flip it again, you are more certain that you have it the right way and you shift it around within the plastic hole in the case until it plugs in.

It's not an issue of poor design on the male USB - it's that there's no fixed orientation for the port. When I plug my mouse into my laptop, I get it right every time. But when I plug it into a desktop, there are (in general) three possible orientations for the port: left, right, up.

Because of this, it doesn't feel like I can ever get it right all the time. If I haven't spent time examining lots of computers, there's no reason why I might think that the 'down' orientation is impossible, and so I have to examine both the computer's port and the USB to get it right the first time. Because of this, it's less effort overall to just attempt whichever orientation I happen to be holding it in. That's where we get to what others described.

I've found checking for the stripe indicating the join in the plug's casing to be a good indicator of insertion orientation (try saying that five times fast).

More generally the plug requires orientation, but doesn't provide much in the way of an indicator at insertion time in the plane of view. Many other plugs do, but they tend to be more elaborate, such as with HDMI and DisplayPort.

It's because they live in the 4th dimension, and the only way to get to the correct side is to turn them 3 times.

Source: Four Dimensional Maths: Things to See and Hear in the Fourth Dimension - with Matt Parker https://www.youtube.com/watch?v=1wAaI_6b9JE