Terror attacks, Crimes, Road security, etc, all these are reasons of installing millions of security cameras everywhere in Europe even in the toilet. On the other hand, the government is actually taxing you for watching something in street. Advertisers pay the government for what you are watching in streets.
McCahill and Norris extrapolated the number of surveillance cameras in Greater London to be around 500,000 and the total number of cameras in the UK to be around 4,200,000. According to their estimate the UK has one camera for every 14 people.