Simple fact. we are all human and make mistakes. There are alos some poor drivers, possibly arrogant. There are probably, in the same proportion, poor and/or arrogant bike riders as well. A trip to London will reveal all. As driver of a German car (hate mail to xxxxxxx!), I work to the advanced standard to which I have been trained, signalling when it will be useful to other road users (including pedestrians). Explained to me thus: "Signalling is like a conversation between you and the person(s) you are informing of your intentions, if there is no-one to inform then you should not inform yoursewlf, just get on with it. The cavat is, that observation must be excellent with a decent standard of driving/cycling."
Not hard.