I believe people are fundamentally unable to comprehend the impact of having anything they do or say available to anybody in the world to witness and critique (probably a reflection of Dunbar's number - as social primates, we've been limited to small social non-anonymous circles for the majority of our evolution).
The issue is that up until the development of the internet (and particularly the social internet), most people weren't subject to this degree of anonynous public exposure. Before twitter and facebook, news outlets were the only exposure, and because of scalability issues, they typically only targeted 'noteworthy' individuals to catch them off guard. So those people learned to hide behind PR individuals, and carefully guard their words and actions when in the public eye.
The issue is that up until the development of the internet (and particularly the social internet), most people weren't subject to this degree of anonynous public exposure. Before twitter and facebook, news outlets were the only exposure, and because of scalability issues, they typically only targeted 'noteworthy' individuals to catch them off guard. So those people learned to hide behind PR individuals, and carefully guard their words and actions when in the public eye.