The same thing with IKEA: I always rely on the manual and just blindly follow the instructions, and gets very frustrated if the instructions miss one step.
Thing I figured out assembling IKEA stuff in the past few years: if it seems like they skipped a step, look carefully at the details in pictures. Perhaps use a magnifying glass. There's going to be only one way to get from step N to step N+1, and all the information to figure it out is there. The drawings of all the pieces, from major parts to tiniest of screws, have accurate details, and there's enough of them to disambiguate the situation.
Basically all other flat pack furniture I’ve ever bought has, but none of the dozen or so ikea items I’ve assembled. It’s part of why I only buy flat pack if it’s ikea, now.
One left out details in the diagrams in each step that they had deemed irrelevant to that step. This apparent attempt at simplifying the instructions stumped me for ages because I kept thinking I'd oriented pieces wrong due to the number of holes in the picture differing from the number of holes in the physical thing.
The other had switched some parts since the instructions were made, and hadn't bothered to update the instructions. This was a bit more obvious, but still kinda irritating for someone like me who is uncomfortable with uncertainty when I believe certainty should be attainable.
Whatever else can be said of IKEA, their manuals and quality control are excellent. I think of them as the McDonald's of furniture — it's never the best product, but it's damn good for the price, and you know exactly what you're going to get.
Following instructions is a good thing. Plenty of people damage stuff when putting it together since it looks obvious, but they usually miss critical details. I would imagine that the people who designed the card scanners had to put a lot of thought into their design simply because they know many people won't read instructions and would do as you suggest: figure out a way to insert [the card] somewhere.
Transit has different considerations though. It is critical that doing the right thing is obvious without reading instructions. Someone might have an important meeting to make and the time to read the instructions (or wait for the person in from of them to read the instructions) means they are late. Or (worse?!?) that time spent in line is annoying enough that someone decides to buy a car. You can somewhat get around this with more fare machines - but they are expensive and take up a lot of space. Fortunately we have human-machine interaction specialists who can tell you how to make a fare machine that is easy to use correctly without needing any instructions.
But why do people make incomplete manuals? If I have a step by step guidance and it doesn't work, because some steps were left out, than this is just a wrong manual!
(I share your frustration)
Ikea, on the other hand, prides itself on user experience. Everything is Ikea-branded, so any complaint will come back to Ikea because the buck stops there. Everything is sold internationally, and they don't want to translate it into a dozen languages, so they have to make clear assembly diagrams. Their entire brand is built around having great assembly instructions!
I mean, it's completely useless for people who has zero experience with camping -- exactly the people who need those instructions and videos and exactly the people who buy these types of tents from Costco.