Therein is the real reason for many cyclists doing it - not because it makes sense (a lot of the time it doesn't) but because there are no consequences. There's no licensing, registration or insurance to cycle on the roads. Many cyclists, and I cycle too, behave accordingly with no consideration for other road users, or pedestrians. Hence many cyclists now cycling on footpaths (illegally) and some getting irritated when they encounter a pedestrian on it!

Most "annoyed drivers" aren't annoyed by a cyclist carefully crossing an empty junction - the annoyance comes in rush hour when others are inconvenienced or it's plain reckless.