As a cyclist who never runs red lights and always tries to communicate clearly where I am going next, there are many cyclists who don't know how to behave in traffic. Yet for every cyclist that behaves like that I will wittness a motorist who is equally wreckless. The only difference being, when the cyclist hits me, I might be hurt, when the motorist hits me I might be dead.
Additional thought here: If you take part in traffic you are taking part in some weirdly formalized form of communications. It is all about "speaking" in a way so others can understand what you like to do. And in traffic you speak by what you do, how you do it and by giving signs.
If you e.g. see pedestrians, brake and continue to roll slowly towards them in your car, you might think: "This is perfectly fine, I saw them!".
But the question is: Did they see that you saw them? If not, then your slowly rolling car communicates; "Yo, I am gonna kill you!" to these pedestrians. This means in that situation the act of stopping is the clearest communication that you saw them.
Using blinkers, hand signs in the way they are intended (to communicate intent) makes also sense. On the highway check your damn mirrors before blinking unless your intent is to ram that car that could be there.
