Human beings are very unpredictable and tend to get creative when it comes to finding loopholes to get away with doing things. If there isn't an explicit and written rule forbidding people from doing something, they will try their luck and see what happens after going through with it.
Typical traffic signs are usually bland and designed to inform you about specific things people need to be aware of. They are pretty straightforward, and taking a single glimpse at them is enough to get all the information you need.
Some have entire sentences in them but are still straightforward and go straight to the point in case more clarification is needed. Besides that, many situations can push people to put up signs warning people about something or forbidding them from doing something.
Some people are too weird and have zero common sense, so it is always important to remind them about the unwritten rules of life they decided to casually obstruct.
The signs in the pictures below are so random and will make a lot of questions pop into your head. The fact that people felt the need to warn people about these things absolutely blows my mind.
The people who put up these signs were probably suffering for a while before they decided that enough was enough and had them made. Whoever thinks that doing any of these things is okay will probably not care that there is a sign warning them not to do them.