With so many things, it is so obvious how to use them that no instructions are required.
Who makes this determination?
Quite often, it is the person who designed it. Wouldn’t you expect that he would know how to use it and that would be obvious to him? Maybe, someone else should be asked.
In the software industry, many seem to have the idea that if a program requires documentation, then it is too difficult to use. This leads to needed documentation being left out. You might find out about a feature or how it works only by being told or by chance.
There is a game called Hack Slash Crawl. It is a simple dungeon crawl game. The instructions are on one screen. There is room for one more line, one that states what the numbers on the spells are for. I only found out by accident that one can use the number keys to start the spells; you do not have to click on the spell icon. In a hard battle, this can make a big difference. A pity it got left out.
Someone thought it was obvious. It was not obvious to me.
I have a small pocket flashlight. Press the button to turn it on momentarily. Fine. I figured that out. However, I was using it one day and pressed rather hard with the result that it broke in my hand. At least, I thought it had. It turns out that it is in two pieces. The flashlight part is attached to the other part with a retractible string. This makes it much more useful, but it never occurred to me before that it worked this way. I really thought that I had broken it, because of no instructions.
The next time you create something for others, how about thinking about how someone who has not seen it before is likely to view it? Some instructions could help.