Signs are indications and directions, they are usually helpful to finding your way and they can also aid in losing your way if you do not interpret the sign well.
A very bad sign would indicate something bad or dangerous ahead, hence it is a warning to folks probably to stay clear.
I noticed people do not always read the signs, most people ignore it on purpose while others are not observant enough to read the signs. And of course you know if you do not read the very bad sign, it is trouble for you.
I will end by saying signs are important to read, they are like directions. You may think it is not helpful but it can be a life saver sometimes.